Skip to main content

Reset your password

Please enter the e-mail address you used to register to reset your password

Note: The verification e-mail to change your password should arrive immediately. However, in some cases it takes longer. Don't forget to check your spam folder.

If you haven't received the e-mail in 24 hours, please contact customerservices@ioppublishing.org

Registration complete

Thank you for registering with Physics World
If you'd like to change your details at any time, please visit My account

Close
Home » Page 1542

Earth’s magnetic field perturbed by ‘electric oceans’, claims researcher

In a radical rethink of accepted geophysics, new research in the US links variations in the Earth’s magnetic field with the ebb and flow of the world’s oceans. Given the practical importance of these field variations in navigation and atmospheric modeling, the implications of this new research extend far beyond academia. However, the idea has already faced strong criticism from some researchers in the geophysics community.

I consider this paper extremely important, although I expect violent opposition from the experts Alex Kostinski, Michigan Technological University

The origin and mechanism of the Earth’s magnetic field are amongst the biggest unsolved questions in the earth sciences. Most geophysicists agree however that the main component of the field — which defines the magnetic poles — is a dipole generated by the convection of molten iron deep within the Earth’s interior. We know, from studying the way magnetic minerals align in volcanic rocks, that this dipole has flipped its orientation every million years or so throughout Earth history.

Given these huge time-scales, sailors and Scouts need not worry about the North Pole suddenly becoming the South, but there is another shorter-term threat to old-fashioned navigation caused by slight drifting of the magnetic field over years-to-centuries. The origin of this “secular variation” is also thought to originate in the molten iron core, due to fluctuations in the established convection pattern. And, although small in comparison with the main dipole field, secular variation can be difficult to predict with effects substantial enough to prompt a revision of the International Geomagnetic Reference Field every five years.

Electric sea salts

Now, Gregory Ryskin of Northwestern University, Illinois, is offering an alternative explanation for the origin of this secular variation. Ryskin believes that electric currents induced in dissolved salts — as ocean waters circulate through the Earth’s magnetic field — can generate secondary magnetic fields strong enough to shift the orientation of the original field. Comparing his own calculations with public geophysical data, Ryskin links circulation in the North Atlantic with observed trends in secular variation over Western Europe.

Scientists have long since known that salt in the ocean can conduct electricity, leading to secondary fields, as the waters chop and change in the presence of the Earth’s magnetic field. In practice, however, it is difficult to gauge the scale of these fields — partly due to the incompleteness of data and the limited precision of computations. Ryskin also suggests that previous measurement of these fields have been somewhat biased by standard theories. “Researchers work backwards — they begin with the assumption that secular variation comes from the core when this is still only a hypothesis.”

Taking a different approach, the physicist looked specifically at the North Atlantic in isolation from other models of the Earth’s field. He calculated the expected variation in magnetic fields between 1995 and 2000 using equations of solute transport and magnetic diffusion, and ocean circulation data from ECCO — a global reference point funded in part by NASA and the National Science Foundation (NSF).

Out of the blue

Ryskin then compared these figures with recorded secular variations in the International Geomagnetic Reference Field (IGRF) — a publicly available resource derived from satellites, observatories and surveys around the world. Publishing his findings in New Journal of Physics, Ryskin finds strong temporal and spatial correlation between his calculated secular variation and the IGRF figures between 1995 and 2000.

The reason this theory is so controversial is that it directly challenges one of the strongest pieces of evidence in the standard model of the Earth’s magnetic field. Secular variation caused by fluid motions in the earth’s outer core is taken by geophysicists as confirmation that the main field also emerges from this region known as the “geodynamo”. As Ryskin asserts in his paper: “If secular variation is caused by the ocean flow, the entire concept of the dynamo operating in the Earth’s core is called into question: there exists no other evidence of hydrodynamic flow in the core.”

Alex Kostinski, an atmospheric physicist at Michigan Technological University told physicsworld.com: “I consider this paper extremely important, although I expect violent opposition from the experts.”

Indeed, some geophysicists believe there are fundamental limitations in this research. “[Ryskin] should compare the required electric currents for the theory with the amplitudes of electric currents that have been measured in the ocean,” said Robert Tyler, an ocean electrodynamics researcher at the University of Washington. Tyler also criticizes the way Ryskin has modeled the spreading of magnetic fields through sea waters. “In a thin conducting shell like the ocean, the diffusion is not through the ocean but along the top/bottom boundaries.”

Despite Ryskin’s bold claims, he is also careful to note that — although he sees strong correlation in his results — this does not prove beyond doubt that all secular variation is due to ocean flow. “In fact, a definitive proof may never be possible, but as the accuracy and completeness of the data continue to improve, and further computations are carried out, sufficient clarity on the issue should be achieved soon,” he writes.

Pnictide superconductor round-up

By Hamish Johnston

If you are wondering what physicists know (and don’t know) about the recently-discovered pnictide superconductors you are in luck — because several leading lights in the field have just published on that very subject.

Over on arXiv Hideo Hosono and colleagues have posted a Progress Report on our understanding of pnictide superconductors.

Meanwhile, Igor Mazin and David Parker have a paper in PRL with a nice description of the “order parameter symmetry mystery” that researchers are currently struggling with — the paper also proposes several Josephson interferometry tests that could clear things up.

Axions could shed light on solar mysteries

If you think the weather on Earth is unpredictable, on the Sun it is far more puzzling. For decades scientists have wondered how its corona — or outer atmosphere — can be so much hotter than its surface, even though they are thousands of kilometres apart. Then there is the question of what powers solar flares, which can shower satellites and astronauts with lethal radiation.

If the logic is correct, then we should have a good chance to directly see solar axions, or axions made in the laboratory by ourselves Konstantin Zioutas, CERN

Now a group led by Konstantin Zioutas at CERN thinks the answer might lie with the “axion”, a hypothetical particle that could also explain the mysterious dark matter that seems to make up most of the universe’s mass. “If the logic is correct, then we should have a good chance to directly see solar axions, or axions made in the laboratory by ourselves,” says Zioutas.

New light on an old theory

Axions were first proposed in the late 1970s to solve an issue in particle physics known as the strong-CP problem. Theory said they would be light with weak interactions — properties that also made them attractive for dark matter. However, despite many experimental searches, evidence for the particles has been thin on the ground.

If axions do exist, physicists think they would be generated in the Sun. The original idea was that microscopic electric fields would convert thermal X–ray photons in the Sun’s hot core into axions, which would then travel outwards. At some point near the surface, magnetic fields would convert them back into X-ray photons, thereby transfering heat from the core to corona. The X–rays could even trigger solar flares.

But although this mechanism would explain the corona’s high temperature at magnetized places, observations show that the Sun does not only emit X–rays radially, as would be expected if they had taken a straight path from their point of conversion. Instead, X–rays seem to come from the surface at all angles. Another problem is that the X–rays ought to have a “black-body” spectrum that peaks at kilo electron volt (keV) energies, whereas in fact the spectrum is more befitting of a power law with no keV peak.

Scattered X–rays

Zioutas’s group thinks it can reconcile axions with such observations. Last year the researchers put forward the beginnings of an idea in which some of the X–rays beneath the surface ionize surrounding matter. The liberated electrons from this ionization would then scatter subsequent X–rays while reducing their energy, causing them to leave the surface in all directions and with a power-law spectrum.

In the researchers’ latest study, “Monte Carlo” computer simulations show that this mechanism could be satisfied by an axion with a mass in the region of 0.02 eV. This type of axion is too light to be detectable with present experiments, though if it does exist it could still serve as a solution to the strong-CP problem, and as a form of “hot” dark matter.

However, the proposal is being met with scepticism by some particle physicists. Aaron Chou, a physicist at Fermilab in the US, says that he has discussed it with Zioutas, but finds it too “unrealistic” to work. “The multiple scattering needed to randomize the directions of the axion–induced X–ray flux destroys the coherence of the process converting axions to X–rays in the first place,” he explains.

“The two requirements of his model — efficient coherent conversion and subsequent randomization of trajectories — appear to be mutually contradictory in that they cannot be simultaneously satisfied, at least not within the context of this model,” he adds.

Upgraded experiment

Zioutas admits that his group’s model has shortcomings, such as the fact that it cannot explain the full intensity of the solar X–rays. Nevertheless, he and Andrzej Siemko, also from CERN, have put in a proposal to CERN management for a more sensitive version of CAST, the present experiment at the European lab that searches for axions leaving the Sun by trying to convert them back into photons in a magnetic field.

The upgrade, which would employ one or two of the spare quadrupole magnets from the Large Hadron Collider and which would cost an estimated CHF 250,000 (£140,000), should be sensitive enough to detect a very light axion.

Zioutas says he will hear the decision about the upgrade within a week.

The research will be published next month in the New Journal of Physics and a preprint is available on arXiv.

Who needs the lunar breakdown services?

Hayes.jpg
Lunar breakdown manual

By Michael Banks

If your car has ever broken down late at night, then the first port of call is, of course, the breakdown services. Failing that, then you can get your hands dirty and turn to the help of the trusted car manual.

One company famous for its owners’ manuals is Haynes who produce them for seemingly every make and model of cars, motorcycles and trucks.

But the publishing firm may now have gone one small step too far. The company has brought out an owners’ manual for the Apollo 11 mission to coincide with the 40th anniversary of Neil Armstrong becoming the first man on the Moon on 20 July 1969.

The manual contains technical illustrations and photographs of the 1969 Apollo 11 model including descriptions of the Saturn V booster rockets as well as the CM-107 command module, the SM-107 service module and the LM-5 lunar module, which took the astronauts to the surface of the Moon and back.

The manual also contains “how it works” and “how you fly it” guides, that give insights into launch procedures, flying and landing the lunar module and even a guide to walking on the Moon.

So if one of the landing legs is a bit stuck or the lunar module hatch is jammed then who needs the 400 000 people who helped build Apollo 11, just get your hands on the Haynes manual for only £17.99.

Tuning the gap in graphene

Researchers in the US have the best evidence yet that the electronic band gap in bilayer graphene can be adjusted by changing an applied voltage. This is unlike conventional semiconductors such as silicon in which the gap is fixed by the material’s crystal structure and chemical composition. The band gap is of great importance when designing semiconductor devices and the ability to adjust its value could make graphene a promising material for future electronic and optical devices.

Graphene is a sheet of carbon just one atom thick and is normally a metal capable of conducting electrons at extremely high speeds — the electrons behave like relativistic particles that have no rest mass. However, under certain conditions it also behaves like a semiconductor and these and other unusual physical properties, means that graphene is often touted to replace silicon as the electronic material of choice in the future.

The electronic band gap is the energy difference between the valence and conduction bands in a semiconductor or metal — and its existence is what allows semiconductor devices to switch electrical currents on and off.

Dialling up light

A semiconductor with a “tuneable” gap that can be changed externally –- by applying a voltage, for example –- could lead to new types of electronic devices, notably lasers where the wavelength of the light could be dialled-up with great precision.

Graphene normally has a band gap of zero, which is related to its massless electrons. In 2007, a team of physicists showed that the electrons in bilayer graphene — a sheet of carbon two atoms thick — appeared to acquire mass when a small external voltage was applied across the sheet. This, they said, is proof that an energy gap could be created and controlled.

Now Feng Wang and colleagues at the University of California at Berkeley have made a more direct mesurement of the band gap in bilayer graphene as the external voltage is varied from 0 to 250 mV at room temperature.

The narrow bandgap range means that it could now be possible to make new types of nanotransistors, nano-LEDs and other nano-optical devices in the infrared range from graphene.

Field-effect transistor

The team made a two-gated bilayer device from graphene. The device, which is a field-effect transistor, is built on a silicon substrate (the bottom gate) and contains a thin insulating layer of silicon dioxide between the substrate and the graphene layers. There is a transparent layer of sapphire (aluminium oxide) over the graphene layers and on top of this, the top gate, made of platinum.

The researchers varied the applied voltage to the gate electrodes and measured how the bandgap changed. They did this by sending an infrared beam (from the Advanced Light Source facility at the Lawrence Berkeley National Lab) into the device and measuring variations in the amount of light absorbed by the graphene layers. The size of the absorption peak in each spectrum gives the exact size of the bandgap at each gate voltage.

The team is now trying to improve the bilayer device for use in high-performance tunable electronics. “We will also try to understand the light emission behaviour from such a tunable semiconductor,” Wang said.

The work was published in Nature.

Flaw revealed in theory of transistor ‘noise’

Engineers in the US and Taiwan have carried out an experiment that they say exposes a serious flaw in our understanding of how transistors work. The research finds that as transistors shrink, the amplitude of electronic “noise” in these devices grows even more than standard theory says it should. The researchers warn that unless our understanding of noise is reviewed, then development of next-generation laptops, mobile phones and other low-power devices could be hampered.

Transistors perform an essential role in electronic devices by amplifying and switching signals, but in order to do this reliably they must be made from highly purified materials. Defects in these materials can — like rocks in a stream — impede the flow of current and cause a transistor to malfunction. As a result, the transistor may fluctuate rapidly between its “on” and “off” states in an effect known as “random telegraph noise”.

What’s all that noise about?

For decades, engineers have been guided by a standard theory that says these fluctuations should become larger as transistors get ever smaller in size, spelling bad news for low-power devices. Recent findings from Kin Cheung and colleagues of the National Institute of Standards and Technology (NIST) in Gaithersburg have shown that the fluctuations may be somewhat larger than predicted and, more importantly, the frequency of their occurrence is inconsistent with conventional noise theories.

These researchers looked specifically at the most common transistor in both digital and analogue circuits — the MOSFET, or the metal–oxide–semiconductor field-effect transistor. Surprisingly, they found that even in nanoscale transistors with widths and lengths of 0.085 micrometres and 0.055 micrometres, the frequency at which the device fluctuates between on and off states does not vary much from larger transistors.

Whilst there have been previous criticisms of the standard model for noise, no-one has been able to prove unequivocally that it is flawed. Cheung and his team now say their results are the most convincing falsifier yet because they have been generated using an “ultra-thin” transistor. With the gate dielectric being only a few molecules thick, they claim they can rule out other potential sources of noise and showcase the first “absolute test” of the standard theory. “We have now used our data to examine all the alternative models and found that, to first order, none of them work,” Cheung told physicsworld.com.

It’s good to talk

If the current model of noise is indeed wrong then this could have a significant impact on the design of low-power technologies. The hope is that consumers will see benefits like mobile phones that can run for a week on a single charge or pacemakers that operate for a decade without requiring a change of batteries. These would require very small and reliable transistors. “We have to understand the problem before we can fix it — and troublingly, we don’t know what’s actually happening,” said Jason Campbell, another of the NIST researchers.

Asen Asenov, an electronics researcher at the University of Glasgow in the UK believes this research addresses a pressing issue in electronics. “RTN has become dramatically important and is a main show stopper to the Flash memory scaling,” he said. Asenov is concerned, however, that the researchers do not take into account that transistors occasionally capture single electrons. “[electron capture] creates localized depletion regions in the semiconductor changing the relative position of the energy level and the conduction band.”

Even though Cheung and his team have taken these accurate readings, physicists will now need to carry out more research in order to confirm what is really going on in ultra-small transistors.

Moonshine could light the way to extraterrestrial life

A new study of sunlight reflected from the Moon should quell any concern that the next generation of space telescopes may not be able to detect signs of life on Earth-like planets orbiting distant stars. That is the view of astronomers in Spain and the US, who have found that it is relatively easy to detect methane and other biologically-significant gases in our own planet by studying the sunlight passing through the Earth’s atmosphere during a lunar eclipse. The measurements raise hopes that NASA’s James Webb Space Telescope, due for launch in 2014, will find evidence for extraterrestrial life.

Astronomers have so far discovered almost 350 extrasolar planets (exoplanets), which orbit stars other than our own Sun. Most of these are “gas giants” similar to Jupiter and it is possible to study what their atmospheres contain if they happen to pass across (or transit) the line of sight between the star and Earth. Astronomers have had some success determining the chemical composition of the atmosphere of a few of these gas giants by studying how they absorb and transmit light.

However, Earth-like planets that could harbour life are much smaller than gas giants, with much less light passing through their atmospheres. Indeed, some computer simulations suggest that next-generation space telescopes such as the James Webb might not be able to detect signs of life — carbon dioxide, water, oxygen and methane — in the atmosphere of such ‘habitable’ exoplanets.

Prominent structures

But now Enric Pallé and colleagues at the Institute of Astrophysics of the Canaries and the University of Central Florida have — for the first time — analysed sunlight after it has passed through Earth’s atmosphere in a transit-like scenario.

The measurements were made during a lunar eclipse in 2008 when the Earth passed between the Moon and Sun — leaving the Moon in near darkness. When this occurred, a small amount of sunlight passed through Earth’s atmosphere, struck the Moon, and then returned to Earth. Some of this light was then collected by Pallé and colleagues on the Canary Islands using the William Herschel and Nordic Optical Telescopes.

The team found that the transmission spectrum for near infrared and visible light contained peaks and troughs corresponding to the presence of oxygen, water, carbon dioxide, and methane in the atmosphere. Although the signals themselves were no surprise, they were more prominent than many astronomers had expected. Indeed, Pallé told physicworld.com that when the team degraded the spectrum to what would be expected from a distant Earth-like exoplanet, the peaks could still be resolved.

Methane high

One unexpected finding is that the signal from methane is particularly high, which is surprising because methane is much less common in the atmosphere than oxygen, water, or even carbon dioxide. As a result, Pallé believes that future telescopes should be optimized to detect methane in addition to oxygen and water.

While the researchers are not certain why the peaks are stronger than many had expected, Pallé believes that it has to do with the very long path through the atmosphere taken by light as it travels tangentially to Earth’s surface. This distance is about 80 times the radial thickness of the atmosphere, and massive computer simulations (as yet unavailable) would be required to understand what happens as it travels such distances.

Exoplanet hunter Giovanna Tinetti of University College London described the research as a “strong and optimistic message” to astronomers planning to use next-generation instruments such as NASA’s James Webb Telescope to search the cosmos for signs of life. “It’s a good sign that we will be able to look at planets slightly larger than Earth,” she says.

Indeed, Tinetti believes that the Hubble Space Telescope could be used today to study a habitable planet transiting a relatively small star. But therein lies the rub — astronomers have yet to discover a suitable candidate for Hubble or even James Webb.

Pallé is optimistic though — he believes that by the time James Webb is working in 2014, the recently launched-Kepler mission will have discovered at least one suitable candidate.

The research is published in Nature.

Name that element

By Michael Banks

If you have ever discovered something such as a new theory or particle then maybe the most fun part would be giving it a name.

So this is exactly what Sigurd Hofmann and his group at the Centre for Heavy Ion Research (GSI in Darmstadt, Germany, are doing now as they rack their brains for a name for the newly discovered element 112.

Hofmann already created one atom of the element, which has 112 protons in the nucleus, in 1996 while at GSI. The element was then temporarily given the catchy name of Ununbium, after “ununbi” which is latin for “one one two”.

However, the International Union of Pure and Applied Chemistry (IUPAC, which develops standards for naming new elements and compounds, stated that the production of any new element must be independently verified at another lab first before it can be officially recognised.

The difficulty was that, at the time, there was no other laboratory in the world that could reproduce the results, meaning a long waiting game for Hofmann.

Then eight years later, in 2004, scientists at the RIKEN Discovery Research Institute near Toyko produced two more atoms of element 112. This finally convinced the IUPAC, but due to other claims on the discovery of element 112 it took the union another five years to investigate and decide who did actually discover it.

In May 2009, an IUPAC report stated that Hofmann’s group did fulfil all the criteria for creating the new element and so Hofmann can now submit a name for the element to the IUPAC.

Once the IUPAC have received the name, they will then publish it on their website for six months giving scientists and the public more than enough time to scrutinise and comment on the new name.

“Our group is presently discussing a name and we hope to present it within the next two or three weeks,” Hofmann told physicsworld.com. “However, this discussion is top secret.”

The GSI lab is getting a lot of practice naming elements as it has already found elements 107 to 111. These are Bohrium (107), Hassium (108), Meitnerium (109), Darmstadtium (110) and Roentgenium (111).

So physicsworld.com readers have you any suggestions what they should name element 112?

In da Vinci's footsteps

By Matin Durrani

All eyes are on the great Italian thinker Galileo Galilei in 2009, in what has been dubbed the International Year of Astronomy.

It is, as you must surely have noticed, exactly 400 years ago since Galileo first turned his telescope to the heavens. As part of our contribution to the IYA, Physics World published a special issue on astronomy in March, which can still be downloaded for free here in case you missed it.

I’ve just come back from holiday in Italy and, although I sadly was not able to make a meeting held in Florence re-examining the ramifications of Galileo’s tiff with the Catholic Church, I did manage to fit in an afternoon in pursuit of that other great Italian polymath — Leonardo da Vinci.

I hadn’t realised that the “Vinci” in his name refers to the place where the great Leonardo was born — a small town in the Tuscan hills roughly equidistant between Florence and Pisa.

The medieval old town contains a fascinating museum, in which some of da Vinci’s famous sketches — including a cycle, an olive-press and a spring-powered cart — have been turned into real objects.

Sadly photography was not permitted inside the building, but you can get some idea of what’s on show by visiting the museum’s website .

What I found perhaps most interesting were some of da Vinci’s ideas for scientific instruments, including a device for measuring the humidity of air. It consisted of a balance with a candle on one side and a ball of cotton wool on the other. As the ball absorbs moisture, it tips the balance in proportion to the amount of water absorbed.

A few miles out of town lies the house where, it is believed, da Vinci was born and where, as a boy, he used to sit and sketch the rolling Tuscan countryside.

Galileo, of course, was born not far off in Pisa in 1564, some 45 years after da Vinci died. What was it about those Tuscan hills that led to two such great minds?

Archaeological dating by re-firing ancient pots

Researchers in the UK have created a new way of dating archaeological artefacts that involves heating ancient pots to unlock their internal clocks. The relatively simple technique could become as important for dating ceramics as carbon dating is for organic materials, say the researchers at the Universities of Manchester and Edinburgh. The team has already dated ceramics from the Roman, medieval and modern periods to a high degree of accuracy, and they are now looking to establish a global research facility for the technique.

The method relies on the fact that fired clay ceramics — like bricks, tile and pottery — start to chemically combine with water as soon as they are exposed to the atmosphere. A big breakthrough came in 2003 when the researchers realized that this process has occurred at a predictable rate throughout history, related to temperatures. Now the researchers have turned their theory into a practical dating method and present their findings in Proceedings of the Royal Society A.

Moira Wilson of the University of Manchester and her team document how “rehydroxlation dating” has so far dated objects up to 2000 years old, and they believe it could extend back as far as 10, 000 years. “Given the number and intensity of [dating] debates in archaeology, there is a huge gap in the field for this,” Wilson told physicsworld.com.

Slow chemical process

Wilson was quick to point out that the water uptake in rehydroxlation is not the same as absorption — it is a much slower chemical process. The researchers established that the rate at which ceramic materials gain extra water in this process obeys a (time)1/4 power law. They calculated that the rate of reaction is independent of atmospheric moisture levels but is governed by the ambient temperature averaged over a ceramic’s lifetime.

The dating procedure involves measuring the mass of a sample of ceramic and then heating it to around 500 degrees Celsius in a furnace, which removes the water. The re-fired ceramic is then weighed immediately, using a highly accurate microbalance, to determine precisely the rate of water recombination. Once the rate is known, the age of the artefact can be extrapolated. “There are no loose ends with this — everything ties in,” said Wilson.

The researchers dated a Roman brick, known to be 2001, as 2000 years old. They also tested a “mystery brick”, with the real age revealed to them only after their testing was completed — they got 340 years, and its known age was 339 to 344. An interesting thing occurred when they tested their technique on a medieval brick from Canterbury: after repeated testing dated it at 66 years, they realized that the intense heat generated during a Second World War blitz had re-fired the brick and effectively reset its clock.

Self-calibrating

At present, the most widely used alternative technique is thermoluminescence, which involves measuring the amount of light given off by a sample because this is related to the dose of radiation an artefact has received across its lifetime. One of the limitations is that it requires a lot of extra information about the archaeological site such as radiation levels, which may not be accessible if artefacts have already been sitting in a museum for many years. Perhaps the most significant feature of this new water-based technique is that — as with radiocarbon dating — it is self-calibrating, based on rehydroxylation alone.

“The time-dependent processes that they have studied looks very interesting,” said Ian Bailiff, an archaeologist at Durham University in the UK. However, Bailiff is a bit sceptical about the reliability of historic temperature records. “The devil is likely to be in the detail – the chronometric mechanism is temperature dependent, and much work may need to be done to obtain calibration data.”

The researchers are now planning to test whether their dating technique can be applied to earthenware, bone china and porcelain. Wilson told physicsworld.com that one of the main difficulties so far has been getting access to ceramics from museums and collectors who are yet to be convinced by the new technique. She believes this situation will improve if her team can establish an international research centre in the UK — she is currently looking into ways of achieving this.

Copyright © 2026 by IOP Publishing Ltd and individual contributors