Ongoing observations of that 2017 merger by the Chandra X-ray Observatory, an orbiting telescope, suggests the latter: that the merged object stuck around, likely for a mere second, before undergoing ultimate collapse.

The evidence is in the form of an X-ray afterglow from the merger, dubbed GW170817, that would not be expected if the merged neutron stars collapsed immediately to a black hole. The afterglow can be explained as a rebound of material off the merged neutron stars, which plowed through and heated the material around the binary neutron stars. This hot material has now kept the remnant glowing steadily more than four years after the merger threw material outward in what’s referred to as a kilonova. X-ray emissions from a jet of material that was detected by Chandra shortly after the merger would otherwise be dimming by now.

While the excess X-ray emissions observed by Chandra could come from debris in an accretion disk swirling around and eventually falling into the black hole, astrophysicist Raffaella Margutti of the University of California, Berkeley, favors the delayed collapse hypothesis, which is predicted theoretically.

“If the merged neutron stars were to collapse directly to a black hole with no intermediate stage, it would be very hard to explain this X-ray excess that we see right now, because there would be no hard surface for stuff to bounce off and fly out at high velocities to create this afterglow,” said Margutti, UC Berkeley associate professor of astronomy and of physics. “It would just fall in. Done. The true reason why I’m excited scientifically is the possibility that we are seeing something more than the jet. We might finally get some information about the new compact object.”

Margutti and her colleagues, including first author Aprajita Hajela, who was Margutti’s graduate student when she was at Northwestern University before moving to UC Berkeley, report their analysis of the X-ray afterglow in a paper recently accepted for publication in The Astrophysical Journal Letters.

The radioactive glow of a kilonova

Gravitational waves from the merger were first detected on Aug. 17, 2017, by the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO) and the Virgo collaboration. Satellite- and ground-based telescopes quickly followed up to record a burst of gamma rays and visible and infrared emissions that together confirmed the theory that many heavy elements are produced in the aftermath of such mergers inside hot ejecta that produces a bright kilonova. The kilonova glows because of light emitted during the decay of radioactive elements, like platinum and gold, that are produced in the merger debris.

Chandra, too, pivoted to observe GW170817, but saw no X-rays until nine days later, suggesting that the merger also produced a narrow jet of material that, upon colliding with the material around the neutron stars, emitted a cone of X-rays that initially missed Earth. Only later did the head of the jet expand and begin emitting X-rays in a broader jet visible from Earth.

The X-ray emissions from the jet increased for 160 days after the merger, after which they steadily grew fainter as the jet slowed down and expanded. But Hajela and her team noticed that from March 2020 — about 900 days after the merger — until the end of 2020, the decline stopped, and the X-ray emissions remained approximately constant in brightness.

“The fact that the X-rays stopped fading quickly was our best evidence yet that something in addition to a jet is being detected in X-rays in this source,” Margutti said. “A completely different source of X-rays appears to be needed to explain what we’re seeing.”

The researchers suggest that the excess X-rays are produced by a shock wave distinct from the jets produced by the merger. This shock was a result of the delayed collapse of the merged neutron stars, likely because its rapid spin very briefly counteracted the gravitational collapse. By sticking around for an extra second, the material around the neutron stars got an extra bounce that produced a very fast tail of kilonova ejecta that created the shock.

“We think the kilonova afterglow emission is produced by shocked material in the circumbinary medium,” Margutti said. “It is material that was in the environment of the two neutron stars that was shocked and heated up by the fastest edge of the kilonova ejecta, which is driving the shock wave.”

The radiation is reaching us only now because it took time for the heavy kilonova ejecta to be decelerated in the low-density environment and for the kinetic energy of the ejecta to be converted into heat by shocks, she said. This is the same process that produces radio and X-rays for the jet, but because the jet is much, much lighter, it is immediately decelerated by the environment and shines in the X-ray and radio from the very earliest times.

An alternative explanation, the researchers note, is that the X-rays come from material falling towards the black hole that formed after the neutron stars merged.

“This would either be the first time we’ve seen a kilonova afterglow or the first time we’ve seen material falling onto a black hole after a neutron star merger,” said co-author Joe Bright, a UC Berkeley postdoctoral researcher. “Either outcome would be extremely exciting.”

Chandra is now the only observatory still able to detect light from this cosmic collision. Follow-up observations by Chandra and radio telescopes could distinguish between the alternative explanations, however. If it is a kilonova afterglow, radio emission is expected to be detected again in the next few months or years. If the X-rays are being produced by matter falling onto a newly formed black hole, then the X-ray output should stay steady or decline rapidly, and no radio emission will be detected over time.

Margutti hopes that LIGO, Virgo and other telescopes will capture gravitational waves and electromagnetic waves from more neutron star mergers so that the series of events preceding and following the merger can be pinned down more precisely and help reveal the physics of black hole formation. Until then, GW170817 is the only example available for study.

“Further study of GW170817 could have far-reaching implications,” said co-author Kate Alexander, a postdoctoral researcher who also is from Northwestern University. “The detection of a kilonova afterglow would imply that the merger did not immediately produce a black hole. Alternatively, this object may offer astronomers a chance to study how matter falls onto a black hole a few years after its birth.”

Margutti and her team recently announced that the Chandra telescope had detected X-rays in observations of GW170817 performed in December 2021. Analysis of that data is ongoing. No radio detection associated with the X-rays has been reported.

In a new report, researchers from the University of Pennsylvania’s School of Veterinary Medicine and Perelman School of Medicine find that, for at least one example of apparent interspecies transmission, this crossing the species boundary did not cause the virus to gain a significant number of mutations.

Writing in the journal Viruses, the scientists identified a domestic house cat, treated at Penn Vet’s Ryan Hospital, that was infected with the delta variant of SARS-CoV-2 subsequent to an exposure from its owner. The full genome sequence of the virus was a close match to viral sequences circulating in people in the Philadelphia region at the time.

“SARS-CoV-2 has a really incredibly wide host range,” says Elizabeth Lennon, senior author on the work, a veterinarian, and assistant professor at Penn Vet. “What this means to me is that, as SARS-CoV-2 continues to be prevalent in the human population, we need to watch what’s happening in other animal species as well.”

The find is the first published example of the delta variant occurring in a domestic cat in the United States. Notably, the cat’s infection was only identified by testing its fecal matter. A nasal swab did not result in a positive test.

“This did highlight the importance of sampling at multiple body sites,” says Lennon. “We wouldn’t have detected this if we had just done a nasal swab.”

Lennon and colleagues have been sampling dogs and cats for SARS-CoV-2 since early in the pandemic. This particular pet cat, an 11-year-old female, was brought to Ryan Hospital in September with gastrointestinal symptoms. It had been exposed to an owner who had COVID-19 — though that owner had been isolating from the cat for 11 days prior to its hospitalization, another household member doing the cat care in the interim.

Working through the Penn Center for Research on Coronaviruses and Other Emerging Pathogens and Perelman School of Medicine microbiologist Frederic Bushman’s laboratory, the team obtained a whole genome sequence of the cat’s virus.

Sequencing revealed the delta variant, more specifically, the AY.3 lineage. The researchers did not have a sample from the infected owner. Comparing the sequence to the database kept by the Bushman laboratory, however, the cat’s virus was nothing out of the ordinary in terms of the sequences of SARS-CoV-2 circulating in the Delaware Valley region at the time.

“When we looked at a random sampling of human sequences from our geographic area, there wasn’t anything dramatically different about our cat’s sample,” Lennon says. “So, our takeaway was that the cat was not infected by a virus that was somehow highly different.”

Not all variants of SARS-CoV-2 have been equally able to infect a wide range of hosts. For example, the original Wuhan strain could not naturally infect mice; later variants gained that ability. Scientists began seeing infections in cats and dogs from the early days of the pandemic, presumably infected through close contact with their owners.

“A main takeaway here is that as different variants of SARS-CoV-2 emerge, they seem to be retaining the ability to infect a wide range of species,” Lennon says.

While this particular case does not raise alarms for the virus acquiring significant numbers of mutations as it moved between species, Lennon and colleagues, including Bushman and Susan Weiss of Penn’s medical school, hope to continue studying other examples to see how SARS-CoV-2 evolves. Penn Vet’s Institute for Infectious and Zoonotic Disease will facilitate this look at human-animal interactions when it comes to pathogen transmission.

“We know that the SARS-CoV-2 is undergoing changes as it passes between to become more and more transmissible over time,” says Lennon. “We saw that with the omicron variant. It’s host-adapting to people. We also want to know, when other animal species get infected, does the virus start to adapt to those species? And for those viruses that may adapt to a different species, do they still infect humans?”

Elizabeth Lennon is the Pamela Cole Assistant Professor of Internal Medicine at the University of Pennsylvania School of Veterinary Medicine.

Lennon’s coauthors on the study were Penn Vet’s Oliva C. Lenz and Stephen D. Cole and the Perelman School of Medicine’s Andrew D. Marques, Brendan J. Kelly, Kyle G. Rodino, Ranawaka A. P. M. Perera, Susan R. Weiss, and Frederic D. Bushman.

Lenz and Marques were co-first authors and Lennon is the corresponding author.

Support for the study came from the Penn Vet COVID-19 Research Fund, the Centers for Disease Control and Prevention (grants BAA 200-2021-10986 and 75D30121C11102/000HCVL1-2021-55232), philanthropic donations to the Penn Center for Research on Coronaviruses and Other Emerging Pathogens, and the National Institutes of Health (grants HL137063, AI140442, and AI121485).

Called environmental DNA or eDNA, the technique searches for trace amounts of genetic material left behind by wildlife.

The scientists, from California State University, CUNY, Wildlife Conservation Society (WCS), and Columbia University, published their results in the journal Frontiers.

The scientists say that eDNA can be used to complement other methods to locate whales and dolphins such as visual observations and acoustic monitoring, and their eDNA detections are some of the most promising to date for detecting whales and dolphins from seawater in the open ocean.

Said the study’s lead author Dr. Elizabeth Alter of California State University: “Determining how cetaceans and other threatened marine animals use coastal habitats is critical to their effective conservation. By generating eDNA data in parallel with survey data, it will be possible to gain a clearer understanding of how this tool can be used in management and conservation contexts to monitor species of conservation concern over large marine ecosystems.”

In addition to finding whales and dolphins, the technique detected baitfish present in the area preyed on by whales and dolphins. The authors say the technique could eventually be used to identify individual animals.

Said Dr. Howard C. Rosenbaum, Director of WCS’s Ocean Giants Program/Senior Scientist NY Aquarium and a co-author of the study: “Innovation and application of new techniques, such as the possibility of using eDNA, that leads to having better information about distribution of whales, dolphins and their prey is so important today, especially where potential impacts in these habitats may be increasing human activities.”

The authors say that eDNA drops to lower levels over time and that additional research is needed to better understand how factors such as behavior and oceanographic conditions contribute to the longevity of eDNA signals.

Though there are some signs of promising recovery for many whale species and populations, whales continue to face a range of modern day threats ranging from ship strikes, to entanglement with nets, to ocean noise.

The Biden-Harris administration, New York State and other states on the eastern seaboard are scaling up massive renewable energy projects to meet energy demands and help address climate change, including a wind energy auction for more than 488,000 acres in the New York Bight. There are many potential impacts from these developments to whales that the environmental community, industry, and state/federal authorities are aiming to address. WCS has been involved at state and national level dialogues as well as developing best practice guidance through the IUCN.

The use of emerging and novel techniques such as eDNA as demonstrated by the results of the current study in the NY Bight and other approaches can offer new insights as to whale presence and their prey in and around lease areas as offshore wind scales up along the eastern seaboard. More broadly, WCS increasingly uses eDNA in its conservation work, detecting critically endangered wildlife such as Swinhoe’s softshell turtle, in the Bolivian Amazon, and in some of the most rugged areas on the planet including Mt. Everest.

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Materials provided by Wildlife Conservation Society. Note: Content may be edited for style and length.

Plastic pollution is a growing global problem, with an increasingly complex mix of plastics found everywhere from the Arctic to Mount Everest.

Simplistic, unhelpful labelling and low recycling rates even in the best-equipped countries are major barriers to tackling this issue.

In a new paper, experts from the University of Exeter and the University of Queensland suggest a new internationally applicable labelling system that moves focus from recyclability to sustainability, is specific to the country and region of purchase and informs the public about plastic additive content.

“We need to empower consumers to make more sustainable choices,” said first author Stephen Burrows, whose research is funded by QUEX Institute, a partnership between Exeter and Queensland.

“Instead of ‘yes-no’ recycling labels, which are often misleading, a ‘sustainability scale’ could take account of recyclability but also other factors such as the environmental cost of production and potential human health risks from additives.

“Requiring packaging to carry region-specific directions for disposal would shift responsibility away from consumers and towards regulators and plastic producers.

“This is vital because the mix of plastic products is so complex and confusing, industry must be responsible for clear, accurate and accessible instructions on how best to dispose of plastic items.

“The same is true for the chemical additives found in many plastics. These chemicals are added to plastics to give them certain properties such as colour, flexibility and fire resistance.

“Requiring producers to list all additives would be a major step towards informing the public and helping them make decisions regarding environmental impact and human health.”

The researchers stress that their recommendations should not detract from the urgent need to use less plastic — especially single-use items.

At present, about 368 million tonnes of plastic is produced worldwide each year.

Estimates of recycling rates vary dramatically. For example, Germany recycles 62% of its plastic waste — well above the European average of 30%.

Meanwhile, China recycles an estimated 25%, while the figure in the USA is just 8%.

Professor Tamara Galloway, from the University of Exeter, said: “Our recommendations for a sustainability scale are designed to reduce some of the confusion around plastic disposal.

“The ultimate aim is to protect the environment and human health from the harmful effects of plastic waste.”

Professor Kevin Thomas, from The University of Queensland’s Queensland Alliance for Environmental Health Sciences and Minderoo Centre for Plastics and Human Health said: “We hope that our recommendations initiate a reassessment of plastics labelling and that implementation of a sustainability scale will allow individuals to make informed decisions in how they use plastics.

“This is just one small necessary step towards helping people help the environment.”

Coffee cup conundrum

Speaking about consumer confusion, Burrows gave the example of PLA (polylactic acid) bioplastic single-use coffee cups.

Many such cups are now labelled as recyclable and compostable — but these are separate processes.

Depending on the composition of the cup, it might be recyclable, but it depends on whether local facilities are equipped to process PLA. So it may not be suitable for your recycling bin.

It might also be compostable — although many such cups can only be broken down in an industrial composter (not in a garden compost heap). So if thrown in general waste, it will end up as more plastic in landfill.

“If someone uses one of these cups then sees a green recycling bin and a ‘general waste’ bin, where should they put it?” said Burrows.

“Most people don’t know, and in fact the answer may depend on several factors not usually indicated.

“Our suggestions for a new labelling system based around a sustainability scale are designed to tackle this confusion.”

The research team included the University of Bath.

“We have built a new system for detecting hydrogen evolution that is the most sensitive in the world,” said Venkatraman Gopalan, professor of materials science and engineering and physics at Penn State. “This tackles a problem that had not been addressed but that is important going forward for materials discovery.”

The tool can be used to screen promising photocatalysts, materials that when placed in water and exposed to sunlight facilitate reactions that split water molecules into hydrogen and oxygen gases, the scientists said. The process, called water splitting, offers a clean and renewable source of hydrogen, but it is inefficient and finding the right photocatalysts to boost hydrogen production has been challenging.

In a study, the team found they could test smaller amounts of photocatalyst material than previously possible and detect very small amounts of hydrogen gas produced, or hydrogen evolution, in the range of tens of nanomoles per hour per tens of milligrams of material. They recently published their findings in the Review of Scientific Instruments.

“If you ranked low in both the categories of hydrogen evolution rate and the mass of the photocatalyst needed, it means it’s a really sensitive system for discovering new photocatalytic materials,” said Huaiyu “Hugo” Wang, a graduate student in the Department of Materials Science and Engineering who led the study and built the system. “And it turns out that our work ranked the best in both categories.”

Developing photocatalysts is an area of intense research. At Penn State, scientists led by Ismaila Dabo, associate professor of materials science and engineering, recently used a supercomputer to narrow a list of more than 70,000 different compounds down to six promising candidates. Another team led by Raymond Schaak, DuPont Professor of Materials Chemistry, synthesized the materials in their laboratory, but creating even small amounts is expensive and time consuming.

“Typical photocatalysts use rare and precious metals such as platinum, which are immensely expensive,” said Julian Fanghanel, a graduate student in materials science and engineering who is co-advised by Dabo and Schaak. “For this project, we are making dozens of samples of materials, so making them in large quantities is impractical, time- consuming and costly.”

Gopalan said the new system will allow scientists to test smaller amounts of these materials and focus efforts on the most promising candidates. But when it came time to test samples, the researchers found commercial equipment was not sensitive enough, so Gopalan and Wang built their own.

“They developed from the ground up a uniquely sensitive gas chromatography setup for the reproducible detection of hydrogen, which was instrumental to the validation of our computational predictions,” Dabo said. “This newly developed capability was a key enabler to confirm the discovery of new photocatalysts for the solar production of hydrogen.”

Unlike the commercial units, the new design can test photocatalysts in their bare state, the scientists said. To be effective, photocatalysts require co-catalysts and other techniques that further improve their efficiency. The gold standard, for example, is titanium dioxide with platinum particles added as a co-catalyst. Photocatalysts without these add-ons are considered bare.

“When we are looking at new materials, we don’t know what the correct co-catalysts will be,” Wang said. “The simple answer is — detecting the bare form is the quickest way to help guide the direction of this materials discovery process.”

Two of the photocatalyst materials tested as part of the study performed better than titanium dioxide did in its bare state, the scientists said. The findings suggest that further study of those materials could yield promising photocatalysts.

“If you have a bare compound that behaved much better than titanium dioxide then we know this is a potential material to optimize,” Wang said. “If we find the right co-catalysts for those materials, we can improve them by orders or magnitude and these materials could eventually be useful in water splitting.”

The scientists said the system is affordable and easy to build from commercially available components. It features a low leakage rate and a small reaction chamber volume size, which allows three orders of magnitude higher detection sensitivity for hydrogen evolution than a conventional gas chromatography system.

“It’s not a brand new technology, it’s just superior engineering,” Gopalan said. “The value of this is that it’s a simple, cost-effective system that anyone can build. And if they do, their research for discovering new photocatalysts is going to go much faster.”

Also contributing from Penn State was Rebecca Katz, graduate student in the Eberly College of Science.

The National Science Foundation supported this research.

To remedy this, a research team co-led by Penn State created a first-of-its-kind methodology for diagnosing printing errors with machine learning in real time. The researchers describe this framework — published in Additive Manufacturing — as a critical first step toward correcting 3D-printing errors in real time. According to the researchers, this could make printing for sensitive devices much more effective in terms of time, cost and computational bandwidth.

“A lot of things can go wrong during the additive manufacturing process for any component,” said Greg Huff, associate professor of electrical engineering at Penn State. “And in the world of electromagnetics, where dimensions are based on wavelengths rather than regular units of measure, any small defect can really contribute to large-scale system failures or degraded operations. If 3D printing a household item is like tuning a tuba — which can be done with broad adjustments — 3D-printing devices functioning in the electromagnetic domain is like tuning a violin: Small adjustments really matter.”

In a previous project, the researchers had attached cameras to printer heads, capturing an image every time something was printed. While not the primary purpose of that project, the researchers ultimately curated a dataset that they could combine with an algorithm to classify types of printing errors.

“Generating the dataset and figuring out what information the neural network needed was at the heart of this research,” said first author Deanna Sessions, who received her doctorate in electrical engineering from Penn State in 2021 and now works for UES Inc. as a contractor for the Air Force Research Laboratory. “We’re using this information — from cheap optical images — to predict electromagnetic performance without having to do simulations during the manufacturing process. If we have images, we can say whether a certain element is going to be a problem. We already had those images, and we said, ‘Let’s see if we can train a neural network to (identify the errors that create problems in performance).’ And we found that we could.”

When the framework is applied to the print, it can identify errors as it prints. Now that the electromagnetic performance impact of errors can be identified in real time, the possibility of correcting the errors during the printing process is much closer to becoming a reality.

“As this process is refined, it can start creating that kind of feedback control that says, ‘The widget is starting to look like this, so I made this other adjustment to let it work,’ so we can keep on using it,” Huff said.

The other authors of the paper were: Venkatesh Meenakshisundaram of UES Inc. and the Air Force Research Laboratory; Andrew Gillman and Philip Buskohl of the Air Force Research Laboratory; Alexander Cook of NextFlex; and Kazuko Fuchi of the University of Dayton Research Institute and the Air Force Research Laboratory.

Funding was provided by the U.S. Air Force Office of Scientific Research and the U.S. Air Force Research Laboratory Minority Leadership Program.

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Materials provided by Penn State. Original written by Sarah Small. Note: Content may be edited for style and length.