Transparent ultrasound chip improves cell stimulation and imaging

Ultrasound scans — best known for monitoring pregnancies or imaging organs — can also be used to stimulate cells and direct cell function. A team of Penn State researchers has developed an easier, more effective way to harness the technology for biomedical applications.

The team created a transparent, biocompatible ultrasound transducer chip that resembles a microscope glass slide and can be inserted into any optical microscope for easy viewing. Cells can be cultured and stimulated directly on top of the transducer chip and the cells’ resulting changes can be imaged with optical microscopy techniques.

Published in the Royal Society of Chemistry’s journal Lab on a Chip, the paper was selected as the cover article for the December 2021 issue. Future applications of the technology could impact stem cell, cancer and neuroscience research.

“In the conventional ultrasound stimulation experiments, a cell culture dish is placed in a water bath, and a bulky ultrasound transducer directs the ultrasound waves to the cells through the water medium,” said Sri-Rajasekhar “Raj” Kothapalli, principal investigator and assistant professor of biomedical engineering at Penn State. “This was a complex setup that didn’t provide reproducible results: The results that one group saw another did not, even while using the same parameters, because there are several things that could affect the cells’ survival and stimulation while they are in water, as well as how we visualize them.”

Kothapalli and his collaborators miniaturized the ultrasound stimulation setup by creating a transparent transducer platform made of a piezoelectric lithium niobate material. Piezoelectric materials generate mechanical energy when electric voltage is applied. The chip’s biocompatible surface allows the cells to be cultured directly on the transducer and used for repeated stimulation experiments over several weeks.

When connected to a power supply, the transducer emits ultrasound waves, which pulse the cells and trigger ion influx and outflux.

To test the setup, Kothapalli and his team cultured bladder cancer cells on the chip. They then inserted fluorescent calcium indicators into the cells to allow researchers to clearly see dynamic changes in cell calcium signaling under the microscope during stimulation.

“Since the cells are directly sitting on the transparent transducer surface, we can confirm that all the cells are equally stimulated at the same time using a single ultrasound stimulus, unlike conventional approaches,” Kothapalli, a co-hire with the Penn State Cancer Institute, said. “And unlike earlier processes, we can get high resolution images of many cells at once in a single field of view, because we are able to see the cells from a close distance.”

Through the bladder cancer cell study, researchers established proof-of-concept for the new transducer setup. But they can extend these findings to use the transducer setup in potential future applications, according to Kothapalli, such as stem cell differentiation, mechanosensitive neuromodulation, drug delivery and the opening of the blood-brain barrier.

“This simple setup will be invaluable for researchers interested in modulating cells and tissues with an ultrasound,” said Pak Kin Wong, professor of biomedical engineering, mechanical engineering and surgery at Penn State and co-author on the paper. “It can be used to explore novel therapeutic ultrasound applications, such as focused ultrasound immunotherapy.”

The ultrasound stimulation chip is low-cost, easy to fabricate, compact and scalable in size, and disposable and reusable, according to Haoyang Chen, first author of the paper and doctoral student under Kothapalli in biomedical engineering.

“It is easy to grow cells on the chip using standard cell culturing methods,” Chen said. “The setup provides controllable stimulation parameters for a variety of experiments and can be imaged with all conventional optical microscopy techniques.”

In addition to Kothapalli, Wong and Chen, other contributors to the study were Peter Butler, Penn State professor of biomedical engineering and associate dean for education and graduate professional programs; biomedical engineering graduate students Ninghao Zhu, Mohamed Osman and Shubham Khandare; and biomedical engineering undergraduate students Ryan Biskowitz and Jinyun Liu.

The study was partially funded by the Penn State Cancer Institute, a Penn State multidisciplinary seed grant, and the National Science Foundation.

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

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Researchers develop 3D imaging technique to understand how dendrites form in batteries

As the world lessens its dependence on fossil fuels, industries and manufacturers are turning to lithium-ion batteries to power the machines that make modern life possible. These batteries power electric vehicles, mobile phones, drones, vacuum cleaning robots and other machines and will be an essential component to the energy transition.

But there’s a problem with lithium-ion batteries: as they age and are charged, they develop dendrites. A research team from the University of Houston is trying to solve the dendrite problem by investigating how these structures grow on batteries. Dendrites are spiky structures that accumulate on the batteries’ anodes. These structures reduce the life of the batteries, hinder their ability to hold a charge and can short-circuit machines potentially causing safety hazards like battery fires.

“By understanding how dendrites grow on batteries, we can identify chemical and physical solutions to prevent the growth of dendrites, which is necessary to develop the next generation of batteries,” said Xiaonan Shan, assistant professor of electrical and computer engineering at UH’s Cullen College of Engineering.

Shan and his team have developed a “novel in-situ” 3D microscopy to image and study the localized electrochemical environments and understand where dendrites start forming in batteries. Using the 3D microscope, small cameras and other computer imaging technology, Shan and his team were able to geometrically map out how a battery initially develops dendrites.

The findings were recently published in the journal Advanced Energy Materials.

“This is significant because most battery researchers traditionally use electrochemical measurements to measure the entire surface or interior battery, so they don’t know what happens inside the battery,” said Shan, who is a corresponding author on the paper. Electrical and computer engineering graduate student Guangxia Feng is the lead author. Most battery companies focus on the materials part of developing batteries, so new materials emphasize performance, he added.

“With this process, manufacturers can theoretically make better performing batteries by focusing on the structural design of batteries that discourages the growth of dendrites,” Shan noted. “And in the next step, we will use this technique to design highly efficient Zn (zinc-carbon) batteries.”

Authors joining Shan and Feng on the paper are Jiaming Guo, Yaping Shi, Xiaoliang, Xu Yang and David Mayerich, all of the UH Department of Electrical and Computer Engineering; and Huajun Tian, Zho Li and Yang Yang, University of Central Florida.

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Materials provided by University of Houston. Original written by Karn Dhingra. Note: Content may be edited for style and length.

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A new platform for customizable quantum devices

A ground-up approach to qubit design leads to a new framework for creating versatile, highly tailored quantum devices.

Advances in quantum science have the potential to revolutionize the way we live. Quantum computers hold promise for solving problems that are intractable today, and we may one day use quantum networks as hackerproof information highways.

The realization of such forward-looking technologies hinges in large part on the qubit — the fundamental component of quantum systems. A major challenge of qubit research is designing them to be customizable, tailored to work with all kinds of sensing, communication and computational devices.

Scientists have taken a major step in the development of tailored qubits. In a paper published in the Journal of the American Chemical Society, the team, which includes researchers at MIT, the University of Chicago and Columbia University, demonstrates how a particular molecular family of qubits can be finely tuned over a broad spectrum, like turning a sensitive dial on a wideband radio.

The team also outlines the underlying design features that enable exquisite control over these quantum bits.

“This is a new platform for qubit design. We can use our predictable, controllable, tunable design strategy to create a new quantum system,” said Danna Freedman, MIT professor of chemistry and a co-author of the study. ?”We’ve demonstrated the broad range of tunability over which these design principles work.”

The work is partially supported by Q-NEXT, a U.S. Department of Energy (DOE) National Quantum Information Science Research Center led by Argonne National Laboratory.

The researchers’ work focuses on a specific group of molecules: those with a central chromium atom surrounded by four hydrocarbon molecules to form a pyramidlike structure.

The molecular qubit advantage

The qubit is the quantum equivalent of the traditional computing bit. Physically, it may take any of several forms, such as a specially prepared atom inside a crystal or an electrical circuit. It can also be a lab-made molecule.

One advantage of a molecular qubit is that, like a tiny 3D-printed gadget, it can be engineered from the bottom up, giving the scientist freedom to tune the qubit for different functions.

“We’re working to change the atomic structure through synthetic chemistry and then learning how those changes modify the physics of the qubit,” said Leah Weiss, a University of Chicago postdoctoral researcher and study co-author.

A molecular qubit’s information is stored in its spin, a property of atomic-level materials. Scientists engineer the spin by adjusting — tuning — the arrangement of the molecule’s electrons, its electronic structure. The information enters the qubit as particles of light, or photons, and is encoded in the qubit’s spin. The spin-encoded information is then translated again into photons, to be read out.

Different photon wavelengths are more suitable for different applications. One wavelength may work better for biosensing applications, another for quantum communication.

The ligand’s the thing

One of the molecular qubit’s key tuning dials is the ligand field strength, the strength of the bonds connecting the central metal atom to the surrounding hydrocarbons.

“The ligand is fundamentally everything. We can intentionally control the way in which the ligand environment influences the spin and rationally control where the emitted photons end up,” said Dan Laorenza, MIT graduate student and lead author of the paper.

Researchers demonstrated that they could exercise remarkably fine tuning over these bonds. Not only that, but they also showed that the ligand field strengths are adjustable over a relatively broad spectrum, while computational simulations performed by researchers at Columbia provided quantum mechanical insight into the ligands’ role in controlling the molecule’s electronic properties.

The light emitted by their chromium qubits spanned an impressive 100 nanometers.

“This is an unprecedented range of tunability for qubits targeting designer applications,” Freedman said.

“Just by keeping the central metal ion the same, which is doing the hard work of the quantum information processing, but tuning the surrounding environment through ligands, you can play around with the properties,” said University of Glasgow’s Sam Bayliss, who co-authored the study while a postdoctoral researcher at the University of Chicago. ?”That’s very hard to do with other systems, like solid-state systems, where you’re essentially fixed at whatever the elemental properties give you.”

A solid-state qubit is created by scooping out a tiny, atom-sized bit of matter from a crystal, and the resulting vacancy is where quantum information is stored and processed. While they have their advantages, solid-state qubits can’t be tuned with the same chemical precision, for example.

“With those, effectively, you get no tuning,” Freedman said. ?”You’re really going from zero to 100 there.”

Laying out the design rules

Approaching the molecule’s design by focusing on its electronic structure — the molecule’s energy levels — rather than its physical structure was key to the team’s discovery.

“Throwing the physical structure out the window and focusing entirely on the electronic structure, which is something that can be achieved across a range of molecular platforms, is really the key innovative detail,” Freedman said.

The researchers spell out the design criteria for building similar molecules in their paper, laying the groundwork for creating new tunable molecular qubits that can be designed toward a future application.

“Having demonstrated the accuracy of our computational methods on these chromium qubits, we can now use the same methods to simplify the screening process,” said Arailym Kairalapova, one of the Columbia researchers who performed the calculations.

“By bringing together the tools of chemistry and physics, it’s possible to start to understand the design rules that will guide the continued improvement of this class of qubits,” Weiss said.

One could custom-design qubits that attach to a biological system and use them for quantum biosensing. Or researchers could architect a qubit to be water-soluble so that it could detect signals in an aqueous environment.

“One of the terrific things about this platform is that, if the molecule doesn’t emit at a certain wavelength, it’s easy for us to go back in the lab, make a new material at a low cost, and see which one gives us the appropriate feature we want,” Laorenza said. ?”We can do this in a few days. It’s not something that takes a really intense, high amount of fabrication.”

The team attributes its success also to innovations in studies of light-matter interactions.

“A few years ago, this was just a dream — to have a set of molecular systems be a novel platform for quantum information science,” Bayliss said. ?”Seeing where we are now is really exciting.”

The team plans to explore different ligand environments to widen the range of photon emission.

“This is now a jumping off point that we hope allows many more chemists to be invited into this space, opening up the work to a much broader range of chemists who could contribute quite a bit to quantum information science,” Laorenza said.

This work was supported by the U.S. Department of Energy Office of Science National Quantum Information Science Research Centers.

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England extends at-home abortion pill offer

Ministers have agreed a six-month extension to the policy that lets women take early abortion pills at home.

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New sickle cell treatment given to first patients in England

Crizanlizumab is thought to cut visits to A&E by 40% for patients with the blood disorder.

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Covid: End of legal need to self-isolate in England

All Covid legal restrictions are over in England, as part of the government’s Living with Covid plan.

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Life may actually flash before your eyes on death – new study

Scientists – who “accidentally” made the first ever recording of a dying brain – saw startling results.

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Cosmic flashes pinpointed to a surprising location in space

Astronomers have been surprised by the closest source of mysterious flashes in the sky called fast radio bursts. Precision measurements with radio telescopes reveal that the bursts are made among old stars, and in a way that no one was expecting. The source of the flashes, in nearby spiral galaxy M 81, is the closest of its kind to Earth.

Fast radio bursts are unpredictable, extremely short flashes of light from space. Astronomers have struggled to understand them ever since they were first discovered in 2007. So far, they have only ever been seen by radio telescopes.

Each flash lasts only thousandths of a second. Yet each one sends out as much energy as the Sun gives out in a day. Several hundred flashes go off every day, and they have been seen all over the sky. Most lie at huge distances from Earth, in galaxies billions of light years away.

In two papers published in parallel this week in the journals Nature and Nature Astronomy, an international team of astronomers present observations that take scientists a step closer to solving the mystery — while also raising new puzzles. The team is led jointly by Franz Kirsten (Chalmers, Sweden, and ASTRON, Netherlands) and Kenzie Nimmo (ASTRON and University of Amsterdam).

The scientists set out to make high-precision measurements of a repeating burst source discovered in January 2020 in the constellation of Ursa Major, the Great Bear.

“We wanted to look for clues to the bursts’ origins. Using many radio telescopes together, we knew we could pinpoint the source’s location in the sky with extreme precision. That gives the opportunity to see what the local neighbourhood of a fast radio burst looks like,” says Franz Kirsten.

To study the source at the highest possible resolution and sensitivity, the scientists combined measurements from telescopes in the European VLBI Network (EVN). By combining data from 12 dish antennas spread across half the globe, Sweden, Latvia, The Netherlands, Russia, Germany, Poland, Italy and China, they were able to find out exactly where in the sky they were coming from.

The EVN measurements were complemented with data from several other telescopes, among them the Karl G. Jansky Very Large Array (VLA) in New Mexico, USA.

Close but surprising location

When they analysed their measurements, the astronomers discovered that the repeated radio flashes were coming from somewhere no one had expected. They traced the bursts to the outskirts of the nearby spiral galaxy Messier 81 (M 81), about 12 million light years away. That makes this the closest ever detection of a source of fast radio bursts.

There was another surprise in store. The location matched exactly with a dense cluster of very old stars, known as a globular cluster.

“It’s amazing to find fast radio bursts from a globular cluster. This is a place in space where you only find old stars. Further out in the universe, fast radio bursts have been found in places where stars are much younger. This had to be something else,” says Kenzie Nimmo.

Many fast radio bursts have been found surrounded by young, massive stars, much bigger than the Sun. In those locations, star explosions are common and leave behind highly magnetised remnants.Scientists have come to believe that fast radio bursts can be created in objects known as magnetars. Magnetars are the extremely dense remnants of stars that have exploded. And they are the universe’s most powerful known magnets.

“We expect magnetars to be shiny and new, and definitely not surrounded by old stars. So if what we’re looking at here really is a magnetar, then it can’t have been formed from a young star exploding. There has to be another way,” says team member Jason Hessels, University of Amsterdam and ASTRON.

The scientists believe that the source of the radio flashes is something that has been predicted, but never seen before: a magnetar that formed when a white dwarf became massive enough to collapse under its own weight.

“Strange things happen in the multi-billion-year life of a tight cluster of stars. Here we think we’re seeing a star with an unusual story,” explains Franz Kirsten.

Given time, ordinary stars like the Sun grow old and transform into small, dense, bright objects called white dwarfs. Many stars in the cluster live together in binary systems. Of the tens of thousands of stars in the cluster, a few get close enough that one star collects material from the other.

That can lead to a scenario known as “accretion-induced collapse,” Kirsten explains.

“If one of the white dwarfs can catch enough extra mass from its companion, it can turn into an even denser star, known as a neutron star. That’s a rare occurrence, but in a cluster of ancient stars, it’s the simplest way of making fast radio bursts,” says team member Mohit Bhardwaj, McGill University, Canada.

Fastest ever

Looking for further clues by zooming into their data, the astronomers found another surprise. Some of the flashes were even shorter than they had expected.

“The flashes flickered in brightness within as little as a few tens of nanoseconds. That tells us that they must be coming from a tiny volume in space, smaller than a soccer pitch and perhaps only tens of metres across,” says Kenzie Nimmo.

Similarly lightning-fast signals have been seen from one of the sky’s most famous objects, the Crab pulsar. It is a tiny, dense, remnant of a supernova explosion that was seen from Earth in 1054 CE in the constellation of Taurus, the Bull. Both magnetars and pulsars are different kinds of neutron stars: super-dense objects with the mass of the Sun in a volume the size of a city, and with strong magnetic fields.

“Some of the signals we measured are short and extremely powerful, in just the same way as some signals from the Crab pulsar. That suggests that we are indeed seeing a magnetar, but in a place that magnetars haven’t been found before,” says Kenzie Nimmo.

Future observations of this system and others will help to tell whether the source really is an unusual magnetar, or something else, like an unusual pulsar or a black hole and a dense star in a close orbit.

“These fast radio bursts seem to be giving us new and unexpected insight into how stars live and die. If that’s true, they could, like supernovae, have things to tell us about stars and their lives across the whole universe,” says Franz Kirsten.

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Colossal black holes locked in dance at heart of galaxy

Locked in an epic cosmic waltz 9 billion light years away, two supermassive black holes appear to be orbiting around each other every two years. The two giant bodies each have masses that are hundreds of millions of times larger than that of our sun, and the objects are separated by a distance roughly 50 times that which separates our sun and Pluto. When the pair merge in roughly 10,000 years, the titanic collision is expected to shake space and time itself, sending gravitational waves across the universe.

A Caltech-led team of astronomers has discovered evidence for this scenario taking place within a fiercely energetic object known as a quasar. Quasars are active cores of galaxies in which a supermassive black hole is siphoning material from a disk encircling it. In some quasars, the supermassive black hole creates a jet that shoots out at near the speed of light. The quasar observed in the new study, PKS 2131-021, belongs to a subclass of quasars called blazars in which the jet is pointing toward the Earth. Astronomers already knew quasars could possess two orbiting supermassive black holes, but finding direct evidence for this has proved difficult.

Reporting in The Astrophysical Journal Letters, the researchers argue that PKS 2131-021 is now the second known candidate for a pair of supermassive black holes caught in the act of merging. The first candidate pair, within a quasar called OJ 287, orbit each other at greater distances, circling every nine years versus the two years it takes for the PKS 2131-021 pair to complete an orbit.

The telltale evidence came from radio observations of PKS 2131-021 that span 45 years. According to the study, a powerful jet emanating from one of the two black holes within PKS 2131-021 is shifting back and forth due to the pair’s orbital motion. This causes periodic changes in the quasar’s radio-light brightness. Five different observatories registered these oscillations, including Caltech’s Owens Valley Radio Observatory (OVRO), the University of Michigan Radio Astronomy Observatory (UMRAO), MIT’s Haystack Observatory, the National Radio Astronomy Observatory (NRAO), Metsähovi Radio Observatory in Finland, and NASA’s Wide-field Infrared Survey Explorer (WISE) space satellite.

The combination of the radio data yields a nearly perfect sinusoidal light curve unlike anything observed from quasars before.

“When we realized that the peaks and troughs of the light curve detected from recent times matched the peaks and troughs observed between 1975 and 1983, we knew something very special was going on,” says Sandra O’Neill, lead author of the new study and an undergraduate student at Caltech who is mentored by Tony Readhead, Robinson Professor of Astronomy, Emeritus.

Ripples in Space and Time

Most, if not all, galaxies possess monstrous black holes at their cores, including our own Milky Way galaxy. When galaxies merge, their black holes “sink” to the middle of the newly formed galaxy and eventually join together to form an even more massive black hole. As the black holes spiral toward each other, they increasingly disturb the fabric of space and time, sending out gravitational waves, which were first predicted by Albert Einstein more than 100 years ago.

The National Science Foundation’s LIGO (Laser Interferometer Gravitational-Wave Observatory), which is managed jointly by Caltech and MIT, detects gravitational waves from pairs of black holes up to dozens of times the mass of our sun. However, the supermassive black holes at the centers of galaxies have millions to billions of times as much mass as our sun, and give off lower frequencies of gravitational waves than those detected by LIGO.

In the future, pulsar timing arrays — which consist of an array of pulsing dead stars precisely monitored by radio telescopes — should be able to detect the gravitational waves from supermassive black holes of this heft. (The upcoming Laser Interferometer Space Antenna, or LISA, mission would detect merging black holes whose masses are 1,000 to 10 million times greater than the mass of our sun.) So far, no gravitational waves have been registered from any of these heavier sources, but PKS 2131-021 provides the most promising target yet.

In the meantime, light waves are the best option to detect coalescing supermassive black holes.

The first such candidate, OJ 287, also exhibits periodic radio-light variations. These fluctuations are more irregular, and not sinusoidal, but they suggest the black holes orbit each other every nine years. The black holes within the new quasar, PKS 2131-021, orbit each other every two years and are 2,000 astronomical units apart, about 50 times the distance between our sun and Pluto, or 10 to 100 times closer than the pair in OJ 287. (An astronomical unit is the distance between Earth and the sun.)

Revealing the 45-Year Light Curve

Readhead says the discoveries unfolded like a “good detective novel,” beginning in 2008 when he and colleagues began using the 40-meter telescope at OVRO to study how black holes convert material they “feed” on into relativistic jets, or jets traveling at speeds up to 99.98 percent that of light. They had been monitoring the brightness of more than 1,000 blazars for this purpose when, in 2020, they noticed a unique case.

“PKS 2131 was varying not just periodically, but sinusoidally,” Readhead says. “That means that there is a pattern we can trace continuously over time.” The question, he says, then became how long has this sine wave pattern been going on?

The research team then went through archival radio data to look for past peaks in the light curves that matched predictions based on the more recent OVRO observations. First, data from NRAO’s Very Long Baseline Array and UMRAO revealed a peak from 2005 that matched predictions. The UMRAO data further showed there was no sinusoidal signal at all for 20 years before that time — until as far back as 1981 when another predicted peak was observed.

“The story would have stopped there, as we didn’t realize there were data on this object before 1980,” Readhead says. “But then Sandra picked up this project in June of 2021. If it weren’t for her, this beautiful finding would be sitting on the shelf.”

O’Neill began working with Readhead and the study’s second author Sebastian Kiehlmann, a postdoc at the University of Crete and former staff scientist at Caltech, as part of Caltech’s Summer Undergraduate Research Fellowship (SURF) program. O’Neill began college as a chemistry major but picked up the astronomy project because she wanted to stay active during the pandemic. “I came to realize I was much more excited about this than anything else I had worked on,” she says.

With the project back on the table, Readhead searched through the literature and found that the Haystack Observatory had made radio observations of PKS 2131-021 between 1975 and 1983. These data revealed another peak matching their predictions, this time occurring in 1976.

“This work shows the value of doing accurate monitoring of these sources over many years for performing discovery science,” says co-author Roger Blandford, Moore Distinguished Scholar in Theoretical Astrophysics at Caltech who is currently on sabbatical from Stanford University.

Like Clockwork

Readhead compares the system of the jet moving back and forth to a ticking clock, where each cycle, or period, of the sine wave corresponds to the two-year orbit of the black holes (though the observed cycle is actually five years due to light being stretched by the expansion of the universe). This ticking was first seen in 1976 and it continued for eight years before disappearing for 20 years, likely due to changes in the fueling of the black hole. The ticking has now been back for 17 years.

“The clock kept ticking,” he says, “The stability of the period over this 20-year gap strongly suggests that this blazar harbors not one supermassive black hole, but two supermassive black holes orbiting each other.”

The physics underlying the sinusoidal variations were at first a mystery, but Blandford came up with a simple and elegant model to explain the sinusoidal shape of the variations.

“We knew this beautiful sine wave had to be telling us something important about the system,” Readhead says. “Roger’s model shows us that it is simply the orbital motion that does this. Before Roger worked it out, nobody had figured out that a binary with a relativistic jet would have a light curve that looked like this.”

Says Kiehlmann: “Our study provides a blueprint for how to search for such blazar binaries in the future.”

Video: https://youtu.be/B_q9tYjvgiY

The Astrophysical Journal Letters study titled “The Unanticipated Phenomenology of the Blazar PKS 2131-021: A Unique Super-Massive Black hole Binary Candidate” was funded by Caltech, the Max Planck Institute for Radio Astronomy, NASA, National Science Foundation (NSF), the Academy of Finland, the European Research Council, ANID-FONDECYT (Agencia Nacional de Investigación y Desarrollo-Fondo Nacional de Desarrollo Científico y Tecnológico in Chile), the Natural Science and Engineering Council of Canada, the Foundation for Research and Technology — Hellas in Greece, the Hellenic Foundation for Research and Innovation in Greece, and the University of Michigan. Other Caltech authors include Tim Pearson, Vikram Ravi, Kieran Cleary, Matthew Graham, and Tom Prince. Other authors from the Jet Propulsion Laboratory, which is managed by Caltech for NASA, include Michele Vallisneri and Joseph Lazio.

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Upcycling plastic waste into more valuable materials could make recycling pay for itself

A new and simple method for upcycling plastic waste at room temperature has been developed by a team of researchers at the Centre for Sustainable and Circular Technologies (CSCT) at the University of Bath. The researchers hope the new process will help recycling become more economically viable.

Plastic waste residing in either landfill or the natural environment currently outweighs all living biomass (4 Giga tonnes), culminating in one of the great environmental challenges of the 21st century. Whilst recycling rates are increasing across Europe, traditional methods remain limited because the harsh remelting conditions reduce the quality of the material each time it’s recycled.

Now researchers at the CSCT have developed a mild and rapid chemical recycling process for polycarbonates, a robust class of plastics commonly used in construction and engineering.

Using a zinc-based catalyst and methanol, they were able to completely break down commercial poly(bisphenol A carbonate) (BPA-PC) beads within 20 minutes at room temperature.

The waste can then be converted into its chemical constituents, namely bisphenol A (BPA) and dimethyl carbonate (DMC), helping to preserve product quality over an infinite number of cycles.

Importantly, BPA recovery prevents leakage of a potentially damaging environmental pollutant, whilst DMC is a valuable green solvent and building block for other industrial chemicals.

Their results are published in ChemSusChem, noting enhanced process efficiency and milder conditions compared to previous methods.

Promisingly, the catalyst is also tolerant to other commercial sources of BPA-PC (e.g. CD) and mixed waste feeds, increasing industrial relevance, whilst being amenable to other plastics (e.g. poly(lactic acid) (PLA) and poly(ethylene terephthalate) (PET)) at higher temperatures.

The team has also demonstrated a completely circular approach to producing several renewable poly(ester-amide)s (PEAs) based on terephthalamide monomers derived from waste PET bottles. These materials have excellent thermal properties and could potentially be used in biomedical applications, for example drug delivery and tissue engineering.

Lead researcher Professor Matthew Jones, at the University of Bath’s CSCT, said: “It’s really exciting to see the versatility of our catalysts in producing a wide range of value-added products from plastic waste.

“It’s crucial we target such products, where possible, to help promote and accelerate the implementation of emerging sustainable technologies through economic incentives.”

First author of the paper, Jack Payne from the CSCT, said: “Whilst plastics will play a key role in achieving a low-carbon future, current practices are unsustainable.

“Moving forward, it’s imperative we source plastics from renewable feedstocks, embed biodegradability/recyclability at the design phase and diversify existing waste management strategies.

“Such future innovation should not be limited to emerging materials but encompass established products too.

“Our method creates new opportunities for polycarbonate recycling under mild conditions, helping to promote a circular economy approach and keep carbon in the loop indefinitely.”

Presently, the technology has only been demonstrated on a small scale, however, the team is now working on catalyst optimisation and scaling up the process (300 mL) with collaborators at the University of Bath. The research was funded by the Engineering and Physical Sciences Research Council.

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Materials provided by University of Bath. Note: Content may be edited for style and length.

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