The Royal Society is piloting a new fellowship programme for Black postdocs to encourage them to stay in science. The initiative offers both financial support and professional development to help these scientists establish an independent research career in the UK. Applications for the pilot scheme open in November.
Data from the Higher Education Statistics Authority (HESA) has consistently shown that people from Black backgrounds are underrepresented at all academic levels in science. The latest HESA statistics reveal that in 2022 only 4% of PhD students were Black. This figure reduces to 2.5% for academic staff and declines even further for staff in senior positions.
In the light of such concerns, in 2021 the Royal Society brought together universities, funders and groups representing scientists of Black heritage to discuss the issues facing them in science. Such problems include a lack of visible role models in academia, a lack of information for individuals who do not have family members who went to university, and the expense and relative instability of academic careers.
It is also known that Black academics in senior roles are more likely than their counterparts of other ethnicities to spend time on mentoring and promoting diversity. Since these activities are not usually considered in traditional metrics of academics’ performance, this could affect career progression and further compound under-representation.
Lasting change
The Royal Society’s new Career Development Fellowships (CDFs) will support scientists with £690,000 in funding over four years, alongside mentoring, training, and networking opportunities.
They will initially be offered to five postdoctoral scientists but, depending on the success of the pilot scheme, similar fellowships may be extended in future to scientists from other under-represented groups.
“Some people may be shocked that a scheme like this is needed in 2023, but the data present a clear case for action on the systemic under-representation of UK scientists from Black backgrounds in academia,” says Mark Richards from Imperial College London who also sits on the Royal Society’s diversity and inclusion committee. “I hope this scheme opens up rewarding careers to many more talented individuals from diverse backgrounds – and when we look back in years to come, we see this as a turning point.”
The existence of a massive galaxy cluster known as El Gordo is not compatible with standard theories of cosmology, say astrophysicists in the UK and Germany. Based on recent Hubble Space Telescope observations and their own simulations, the researchers claim that the cluster’s formation would be better described by an alternative theory of gravity known as Modified Newtonian Dynamics, or MOND.
In standard theories of cosmology, galactic clusters form at the nodes of filaments of dark matter within the cosmic web. This formation mechanism implies that they should all grow at approximately the same average rate as matter falls into the nodes. El Gordo, however, is unusually massive for its age. The latest Hubble Space Telescope observations used weak gravitational lensing to pin its mass at 2.13 × 1015 solar masses, but its redshift is just 0.87, and we see it as it existed 6.2 billion years ago – around a billion years after it formed from the merger of two smaller clusters.
The new simulations suggest that to replicate El Gordo’s observed morphology, temperature and X-ray luminosity, these smaller clusters – which should, according to standard theories, be filled with dark matter – must have collided with a velocity of at least 2500 kilometres per second. This is faster than gravitational models of dark matter can explain, leaving the authors of the latest research questioning the role of this still-mysterious substance in the standard model of cosmology, which cosmologists call ΛCDM or LCDM (where Λ or L refer to dark energy, and CDM stands for cold dark matter).
“Considering the wide range of prior simulations that tried to replicate El Gordo with a slower collision but found that it does not really look realistic, I would argue that it cannot really work in LCDM,” says Indranil Banik, a research fellow at the University of St Andrews and a co-author (with Elena Asencio and Pavel Kroupa of the University of Bonn) of a paper in The Astrophysical Journalon the new simulations.
A tension with standard cosmology
This is not the first time that Asencio, Banik and Kroupa have found incompatibilities between El Gordo and LCDM. In 2021, they described a model based on an earlier mass estimate for the cluster as a “massive blow” to LCDM. They also note that El Gordo is not the only cluster that has come under scrutiny for a potential conflict with LCDM.
“There are definitely other clusters that have already been observed and which also show some tension with LCDM,” Asencio tells Physics World. Examples include the Bullet Cluster and Abell 1758, which is 3.2 billion light-years away and has a total mass of 3.3 × 1015 solar masses.
Different points of view
In truth, while the trio describe their results as in “tension” with LCDM, they are actually arguing that dark matter does not exist, and that MOND should replace it as the basis of a new, alternative cosmology to LCDM. Douglas Clowe of Ohio University in the US is among those who doubt the evidence is strong enough to require such a significant shift, and he thinks the new results could have a simpler explanation.
Composite colour image of the interacting galaxy cluster El Gordo, showing X-ray light in blue, optical data in red, green, and blue, and infrared emission in red and orange. (Courtesy: X-ray: NASA/CXC/Rutgers/J Hughes et al; Optical: ESO/VLT & SOAR/Rutgers/F Menanteau; IR: NASA/JPL/Rutgers/F Menanteau)
“The systematic error in infall velocity measurements are often quite high and frequently explain such results,” he says. Clowe’s own analyses of both the Bullet Cluster and Abell 1758 concluded that whatever is producing the anomalous extra gravity is displaced from the clusters’ visible matter and their intra-cluster plasma. The logical inference, he says, is that unseen dark matter, and not a modification to the gravitational force of visible matter, must be the culprit.
Richard Massey of Durham University, UK, agrees that anomalies in observations of the Bullet Cluster have been resolved in favour of dark matter. “The ‘tension’ there just tuned out to be a different point of view from the people who had taken the images to those who interpreted it,” he says.
This “different point of view” is often at the heart of the debate between proponents of dark matter and of MOND. For Massey, the key to resolving it will be to develop a more joined-up approach, one in which the scientists running the telescopes and those running the supercomputer simulations that model what the telescopes might see work together to interpret complex data.
“This team is trying to act as interlocutors between groups, but aren’t directly involved in any of the aspects of data collection, analysis or interpretation,” says Massey. “They have helpfully started a dialogue, but I’d like to see a more joined-up analysis before I put a great deal of trust in the conclusions.”
A cluster too soon?
For their part, Asencio, Banik and Kroupa say the very existence of El Gordo during this era of cosmic history is evidence that something is amiss. “The El Gordo cluster having formed and already collided by a redshift of 0.87 shows that the universe forms structure far more rapidly and efficiently than predicted by LCDM,” Kroupa tells Physics World.
Kroupa doesn’t pull his punches. For him, clusters such as El Gordo are convincing evidence that dark matter is a fantasy, one that could have far-reaching repercussions. “Such galaxy cluster collisions are in complete disagreement with LCDM while being in rather natural agreement with the MOND cosmological calculations done until now,” he says. “We need to develop a new, realistic cosmological model – we are talking about a paradigm shift that happens in science only once every 100 to 200 years.”
Proton paintings The original artwork and recreated “paintings” in isodose colour wash and dose colour wash for Girl with a Pearl Earring by Johannes Vermeer (top row), The Starry Night by Vincent van Gogh (middle row) and The Scream by Edvard Munch (bottom row). (Courtesy: Medical Dosimetry 10.1016/j.meddos.2023.08.006)
Intensity-modulated proton therapy (IMPT) is an advanced cancer treatment technique that uses narrow pencil-like beams of protons – painted spot-by-spot and layer-by-layer within the patient – to deliver radiation in highly complex dose patterns. Combined with sophisticated treatment planning techniques, IMPT can shape the proton dose to match the targeted tumour with unprecedented accuracy, maximizing the destruction of cancer cells while minimizing damage to nearby healthy tissue.
Looking to showcase the impressive power of IMPT to create intricate dose distributions, medical physicist Lee Xu from the New York Proton Center came up with an unusual approach – he used proton pencil beams to recreate a series of well-known paintings as treatment plans, effectively using the protons as a paintbrush.
“When I first entered this field, I remember looking at treatment plans and being amazed at how beautiful they were. They really looked like works of art to me,” Xu tells Physics World. “As I spent more and more time observing treatment planning, I realized how similar dosimetrists were to artists. The only difference really, was in the medium they used and the canvas they applied the medium onto.”
Xu chose five well-known paintings – Girl with a Pearl Earring by Johannes Vermeer, The Starry Night by Vincent van Gogh, The Scream by Edvard Munch, Composition with Red, Blue and Yellow by Piet Mondrian, and Son of Man by René Magritte – to recreate in the Eclipse v16.1 treatment planning system, sharing the resulting images in Medical Dosimetry.
To generate each “painting”, the planning system used clinical protons with energies of 70–250 MeV to deposit “paint” (radiation dose) onto a “canvas” (a water phantom), with a total prescription of 100 Gy in 50 fractions. Each treatment plan employed between one and six proton fields directed onto the front of the canvas, with the isocentre placed at a depth of 10 cm.
The process begins in a similar manner to a traditional artwork – by creating a preliminary sketch on the canvas to determine the overall layout, in this case using the 2D brush tool in Eclipse’s contouring workspace. Next, key elements such as the sky and the ground are delineated as contours and divided into separate structures to represent different colours, tones and textures. In some cases, Xu used a final subdivision into even smaller structures (up to 65 for the most complex painting) to reflect more intricate details.
Xu assigned different colours to various isodose levels between 0 and 100 Gy in intervals of roughly 300 cGy. He then optimized the treatment plans to deposit doses within the canvas that achieved the desired colour in each region. Xu notes that the final dose distribution was calculated using the same proton convolution-superposition algorithm employed in his clinic.
“After I became acquainted with pencil-beam scanning proton therapy, I realized the possibilities for dose painting using protons were near limitless,” says Xu. “I really wanted to see how far I could push it, and what better way than to recreate some of my favourite paintings using proton beams. While I’ve had this idea for almost five years now, I only recently had the time and patience to bring it to fruition.”
The final recreations exhibited a marked resemblance to the original artworks with sufficient resolution to elucidate fine details. Xu notes that each painting is actually a three-dimensional work of art and can be viewed at multiple depths within the water phantom.
As well as being an impressive demonstration of cutting-edge medical technology, the paintings serve an additional purpose. Xu envisages that they could act as an educational tool, to help patients undergoing treatment understand the general principles of proton therapy, or even to help medical and medical physics students better understand proton physics and dosimetry by using a series of annotated paintings.
“I hope this paper showcases how far we’ve come since the days of 2D planning and how modern technology has allowed us to provide highly targeted care that is specific to each patient,” Xu adds. “I also hope this work serves as a reminder to all of us within the fields of radiation oncology and medical physics that while we often consider ourselves scientists or clinicians, deep down we are also artists; and without art, our field wouldn’t be the same.”
A new and highly accurate electrospray technique could be used to create coatings of biomaterials and bioactive compounds for medical applications such as vaccinations. The technique, which was developed by researchers at Rutgers University in the US, is better at targeting the region being sprayed than existing methods and provides increased control over the electrical discharge of the charged particles being deposited. The result is that more of the spray ends up coating the area of interest.
Electrospray deposition involves applying a high voltage to a flowing liquid to convert it into a mist of fine particles with charged surfaces. As these charged particles travel towards the target area, they evaporate and deposit a solid precipitate.
While the technique is efficient at coating massive objects such as car bodies, it is much less so for smaller targets. This is because charge builds up around the target and effectively screens it from the “view” of the spray. Without a target, the spray destabilizes into a bigger, less directed mist, explains Jonathan Singer, a materials engineer at Rutgers and the leader of a study on the new technique.
Droplets “see” the target
In the study, which is detailed in Nature Communications, Singer and colleagues kept the droplets directed at the target by placing a large, grounded support underneath it that is isolated from the spray droplets by insulating coatings. “The purpose of this support is to stabilize the electric field and make sure that any droplets that approach the target ‘see’ it,” Singer explains.
The team demonstrated this technique with several materials, including biocompatible polymers, proteins and bioactive molecules, and on both flat and microneedle array targets, which are complex surfaces. These bioactives can be costly, but their clinical usefulness means they are increasingly being employed to coat medical devices such as stents, defibrillators and pacemakers that are implanted in the body. More recently, they have also appeared in products such as patches that deliver drugs and vaccines through the skin. In either case, being able to deposit them more efficiently means wasting less of the precious material.
“Current methods only achieve about 40% efficiency,” Singer notes, “but by incorporating different strategies to manipulate the ‘charge landscape’ of the particles being deposited, we can produce coatings that contain almost 100% of the sprayed material on a surface measuring 3 mm2.”
High efficiencies in a wide range of materials
As well as being more efficient, the new technique is more flexible than existing methods, which often require a lot of optimization of the material’s formulation to get the right viscosity and surface tension for a specific film. “One of the things we showed in our work is that we can achieve high efficiencies for coating a wide range of materials, including small molecule drugs, vaccines and polymers,” Singer says. “This means that we can use a wider range of formulations and focus that formulation development on whatever that function is.”
In the case of vaccines, for example, this might mean focusing on formulations that are better at getting the drug into target cells, he tells Physics World.
Until now, the team’s research has focused on dry coating microneedle arrays with DNA vaccines, in collaboration with their sponsor GeneOne Life Science Inc., which manufactures small-molecule drugs and vaccines. “Microneedle arrays are easier to administer and less painful than typical injections, and dry-coated drugs are generally more stable,” explains Singer. “This means they could be transported to remote or underserved populations. The fact that the coatings can be deposited on complex surfaces should also allow for other applications, such as more permanent implants like vascular stents that are treated with drugs to prevent clotting.”
Further down the line, being able to target patterned electrode arrays will also enable applications in microelectronics in so-called “lab-on-chip” diagnostics, he adds.
The next steps for this technology are to demonstrate its effectiveness in animal experiments and ultimately in humans. “We are also continuing research into translating the hardware we need to transfer the process from the lab bench to a more commercial product,” says Singer, adding that university-industry collaboration has been crucial for speeding their past work into clinical trials.
The phrase “I was like a child in a sweet shop” is probably the best way to describe my recent visit to the Harwell Science and Innovation Campus. Set in the bucolic Oxfordshire countryside about 60 miles west of London, the site is home to several of the UK’s National Laboratories, which are run by the Science and Technology Facilities Council (STFC). Indeed, one of the best parts of my job is visiting places like Harwell and chatting with the brilliant people who work there.
As well as touring several labs, I also interviewed the particle physicist Dave Newbold, who is the STFC’s executive director, national laboratories science and technologies. You can listen to that wide-ranging interview in an upcoming episode of the Physics World Weekly podcast.
But first, I am going to devote a series of blog posts to the facilities I toured at Harwell. First up is the ISIS Neutron and Muon Source, where I was given a fascinating tour by Philip King, Alison Oliver and Russell Ewings.
Two targets
King was quick to point out that ISIS is not only the first spallation source used for neutron science – it is the only spallation source that employs two targets. You may be wondering what a spallation source is – but let’s back up a bit and explore why beams of neutrons – and indeed muons – are used across a wide range of sciences.
The neutrons created at ISIS and other neutron-science facilities are slow moving and therefore have de Broglie wavelengths that are on par with the distances between adjacent atoms in liquids and solids. As a result, beams of these neutrons can be used in diffraction studies of the structure of materials. Unlike X-rays with comparable wavelengths, neutrons can travel much further into most materials so they are a more effective probe of bulk properties.
Neutrons can also collide with atoms in a sample and exchange energy, which means that they can probe the vibrational properties of matter. What is more, neutrons also interact magnetically with materials – so they can probe magnetic properties.
Directional decay
And what about muons, what are they good for? Muons are subatomic particles with magnetic spin. When they are implanted in a sample, the muons’ spins are affected by the local magnetic properties of the material. The muons then decay to a positron, which is emitted from the sample in a direction that is indicative of the spin of the muon. Therefore, by detecting the emitted positrons, information is gleaned about the magnetic properties of the sample.
At ISIS, neutrons and muons are created by firing pulses of 800 MeV protons at solid targets and the protons are created by a synchrotron accelerator at the heart of the facility. According to the SFTC, about 1200 experiments per year are done at ISIS. These involve about 3000 researchers from the UK and around the world, and result in about 600 publications per year.
Neutron science facilities like ISIS have a special place in my heart because a lifetime ago when I was an undergraduate physics student, I spent a glorious summer at Chalk River Laboratories – which in 1988 was run by Atomic Energy of Canada (AECL). Located on the shore of the Ottawa River, and on the edge of the Canadian wilderness, Chalk River was home to the AECL’s Neutron and Solid State Physics Branch. The branch has included some of the world’s most eminent neutron scientists – something that I admit I was oblivious to when I first arrived.
Down by the river: Chalk River Laboratories as seen from the Ottawa River. The brick building in the centre is NRU. (Courtesy: Padraic Ryan/CC BY-SA 3.0)
I don’t think that I accomplished much scientifically that summer. However, I was lucky because my supervisor back at the University of Guelph – the neutron-scattering pioneer Peter Egelstaff – allowed me to help out with some of the other research being done at Chalk River’s National Research Universal (NRU) reactor neutron source.
Some of my many fondest memories include rotating a large industrial component in a neutron beam to look for defects, and learning how neutrons are used to study biological membranes. As I discovered at Harwell, both of these things – and much more – are done at ISIS today.
But one of the best parts of being at Chalk River was the group tea/coffee breaks, for which attendance was compulsory. That summer, the hot topic of discussion at these breaks was the relative merits of spallation neutron sources compared to reactor sources like NRU. I can remember having the spallation process carefully explained to us students – and it sticks in my mind to this day that the term is derived from the word “spall”, which means to chip away at something.
During my visit to Harwell, I learned that just a few years before my summer stint at Chalk River, ISIS had opened as the world’s first spallation source for neutron science. I’m guessing that by 1988, the first scientific papers from ISIS were being published, piquing the interest of the global neutron community. So, 35 years and a visit to ISIS later, I now know why spallation was such a hot topic that summer on the banks of the Ottawa River.
“I always preferred science or maths over other subjects in school,” says Silvia Vignolini, “but I had no idea what a physicist actually did.” Growing up in a small town outside Florence, Italy, Vignolini’s father in fact wanted her to study a subject that would lead to “a proper job” and her route into physics occurred rather by chance. “I had a great chemistry teacher, who would make us read science books and present them to the class.”
As a result, her interest in the subject – and astrophysics in particular – was piqued after Vignolini gave a talk on Stephen Hawking’s A Brief History of Time. Despite not understanding much of the science discussed in the book, she refused to give up and turned to a friend who was studying physics to help her understand the unfamiliar concepts. She then started devouring other science books, including Bertolt Brecht’s biography of Galileo.
But as it turns out, Vignolini’s foray into physics rested on another chance comment too. “I was wearing a large jumper from my mum and black trousers – I had this grunge-style look – and someone said I’d make a really good physicist,” she recalls with a laugh. “I don’t think I’m a particular genius, but I never questioned my decision or asked myself if I would be good enough. I thought studying physics was cool, so that’s what I did.”
I wanted to do astrophysics but it wasn’t as hands-on as I thought, so I ended up going for light and optics.
She went on to study physics at the University of Florence, gaining a bachelor’s and Master’s degree in the subject. “I wanted to do astrophysics but it wasn’t as hands-on as I thought, so I ended up going for light and optics,” Vignolini explains. But as the first person in her family to go to university, her parents did not agree with her choice. In fact, her father had hoped she’d do economics and take over the finances of the family shop. “He thought physics would be a waste of time as I’d never find a job and, back then, I couldn’t really explain what physicists did.”
In 2009 Vignolini was offered a PhD in optical physics at the European Laboratory for Non-linear Spectroscopy (LENS) at the University of Florence. “They told me it would be like my Master’s thesis but would be three years and paid” she recalls. “So I said, ‘why not?’” Lured by the opportunity to do more research and go to conferences, Vignolini admits she was rather naïve about what a PhD would entail. “I wasn’t like the PhD students that I encounter now where they see this as a career.”
New encounters
After her PhD, Vignolini was encouraged to go abroad and ended up doing a post-doc in the Cavendish Laboratory at the University of Cambridge in the UK. Working with the soft-matter physicist Ullrich Steiner, she started studying the optical properties of plants and animals whose vivid colours come not from pigments or dyes but from nanoscale structures that scatter light. But switching fields wasn’t easy. “I thought I’m going because the lab looks really cool but wasn’t sure if the project was going to work, so I insisted with my supervisor to have a second, more physics-based project that involved developing new optical materials.”
As it turned out, moving to the UK proved a great success, helped by the different approach to science compared to back home. “I felt valued and enormously motivated as people were grateful for what [I did]”, she says. “In Italy you usually have to be grateful to people to be able to work.” She also credits Cambridge for opening up her mind and changing how she does science. “Now, I only look at the question, and the tools and people I need to solve the problem.”
In 2014, after receiving a Philip and Patricia Brown Next Generation Fellowship from the University of Cambridge, Vignolini formed her own research group within Cambridge’s chemistry department. Her team set out to build artificial photonic structures using natural materials, with the hope of creating novel biodegradable materials that could replace traditional, potentially hazardous colourants used in, say, cosmetics, textiles and security tags. “So far, we have worked intensively to make more sustainable pigments.”
As a new group leader, she was helped by winning a David Philip fellowship from the Biotechnology and Biological Sciences Research Council (BBSRC) in 2013 to study how plants produce structural colours. She also won a “starting grant” from the European Research Council in 2015. However, Vignolini acknowledges that finding group members was challenging because the research is slow and requires scientists who combine a knowledge of physics, chemistry and biology.
All that glitters Work carried out by Silvia Vignolini and her colleagues on replicating the structural colours of cellulose has led to a spin-off firm being set up to make plant-based coloured pigments and glitters. (Courtesy: Droguet, B.E., Liang, HL., Frka-Petesic, B. et al. Large-scale fabrication of structurally coloured cellulose nanocrystal films and effect pigments. (Nat. Mater.21 352). doi.org/10.1038/s41563-021-01135-8)
Finding ways to replicate natural structural-colour has massive commercial potential and environmental benefits. “We often don’t really think about how colours are produced, but they come from synthetic pigments and dyes and have a huge environmental cost,” says Vignolini. “They have high use of water and energy, can exploit critical metals or include carcinogenic chemicals, and lots of waste material ends up in waste water and our ocean.”
Keen to commercialize research carried out in her lab, in 2022 Vignolini helped co-found two spin-out companies. Sparxell is headed by Benjamin Droguet – one of Vignolini’s former PhD students – and is trying to replicate the structural colours of cellulose on a large scale to make plant-based coloured pigments and glitters (Nature Materials 21 352). The other company – Impossible Materials – is being led by a former post-doc in her group, Lukas Schertel, and is commercializing the white pigments inspired by the South-East Asian Cyphochilus beetle (ACS Nano 16 (5) 7373).
Natural wonder Another company spun off from Silvia Vignolini’s research is trying to commercialize pigments inspired by the South-East Asian Cyphochilus beetle, which is covered in unusually bright white scales across its whole exoskeleton. (Courtesy: iStock/Elisa Irmalia)
Vignolini is happy that her research is making its way into the real world but she is also proud of her group’s students and postdocs making an impact. “I hope that our technology can be positive for the planet and the problem of global warming, and to continue bringing the best out of people,” she says. “Mentoring is the most important part of my job.”
Directing a department
In January 2023, Vignolini was appointed director of a new department at the Max Planck Institute of Colloids and Interfaces (MPICI) in Potsdam, Germany, dedicated to sustainable and bio-inspired materials. The first female director at the MPICI, she is currently travelling back and forth between the UK and Germany while also raising two toddlers. “I didn’t expect the job would be different, but actually it is. In my research group, I enabled other people and here it’s building something for others,” she says.
Science disciplines don’t have to have distinct boundaries, they are all intertwined and you have to keep an open mind
While still in the early stages of her career in Germany, Vignolini is building an electron microscope room from scratch and searching for a new team. “It takes time to find the right people. Some members of the Cambridge group will move here from September and others are looking for other positions,” Vignolini explains. “The plan is to move 100% here, but I am finishing up some projects in Cambridge and still mentoring students.”
In Germany, Vignolini will also be developing another field of research called “sym-bionic matter”, which involves looking at how organisms co-operate to harvest and manipulate light. There’s one species of green sea slug, for example, that sequesters living chloroplasts from the alga it eats so that photosynthesis can carry on inside the slug’s cells. “Science disciplines don’t have to have distinct boundaries, in fact, they are all intertwined and you have to keep an open mind,” she says. “I don’t really see what chemistry or physics or biology is anymore; I take a wider approach and believe that is how science knowledge progresses.”
Planetary scientists in the US have traced carbon on the surface of Jupiter’s moon Europa to the icy ocean beneath it, revealing new information about the ocean’s nature and origin. The discovery raises astrobiologists’ hopes that the carbon, which exists in the form of carbon dioxide, could stem from biological processes taking place under the ice. However, a search for water plumes bursting out of Europa’s surface came up empty, and scientists involved in the observations say that better measurements will be needed to distinguish between biological and geological sources of carbon.
We know there’s an ocean on Europa thanks to Jupiter’s immense magnetosphere, which induces a magnetic field within the salty liquid water. Astrobiologists have speculated about the habitability of this ocean for years, but it is difficult to study because it is buried beneath the moon’s 23–47-kilometre-thick ice shell.
Carbon chaos
Instead of digging through the ice to probe the ocean directly, the latest studies used the Near-Infrared Camera (NIRCam) and Near-Infrared Spectrometer (NIRSpec) on the James Webb Space Telescope (JWST) to bring the ocean closer to us. Among the features on Europa’s surface are regions full of irregularly shaped blocks crisscrossed by discoloured ridges. Known as chaos terrain, these regions have been interpreted as sites where material from the ocean wells up and reaches the surface, and it’s here that scientists in two separate teams hunted for evidence of the ocean’s composition.
The data showed four strong spectral signatures of carbon dioxide in Tara Regio, which is an 1,800-kilometre-wide area of chaos terrain on Europa’s leading hemisphere. The scientists also identified a weaker signal of carbon dioxide in another area of chaos terrain called Powys Regio.
Signatures of carbon dioxide at spectral wavelengths of 4.25 and 4.27 microns brought particular attention. While the latter is the expected infrared emission of pure carbon-dioxide ice, the former suggests a mixture of carbon dioxide and other molecules.
One of the teams, led by Geronimo Villanueva of NASA’s Goddard Space Flight Center, identified this mix as water ice laced with carbon dioxide and methanol. Intriguingly, laboratory experiments suggest that the 4.25-micron signature could stem from salts being brought to the surface from the ocean and becoming irradiated. The carbon dioxide-water ice-methanol mixture then either forms a thin film around the salt crystals or is trapped inside them.
A primordial origin
The ratio of carbon-12 to carbon-13 isotopes on Europa is also of profound interest. Villanueva’s team measured this ratio as 83 (+/–19), placing it firmly within the bounds of ratios measured on Saturn’s moons, the near-Earth asteroid Ryugu visited by Japan’s Hayabusa-2 mission, and Earth, which has a carbon-12 to carbon-13 ratio of 89 for inorganic carbon (that is, carbon not bonded to hydrogen). This commonality suggests that, unlike water, which occurs in different isotopic ratios on different bodies, the carbon built into the worlds and moons of our solar system comes from the same source.
“The isotopic values, within the accuracy that we achieved, are indeed consistent with that of other moons and also of some primordial materials,” Villanueva tells Physics World.
As such, measurements of Europa’s carbon provide more information about the composition and distribution of materials in the proto-stellar disc that formed the solar system some 4.5 billion years ago.
An oxidized ocean
The second team, consisting of Samantha Trumbo of Cornell University and Michael Brown of the California Institute of Technology, focused on the origins of Europa’s carbon. Since the JWST detected no complex organic molecules on Europa’s surface, Trumbo and Brown say this eliminates any chance that the carbon dioxide formed via photodissociation of those organics as the radiation environment around Jupiter breaks them apart. Instead, the observations indicate that the carbon was already in the form of carbon dioxide when it reached the surface, suggesting that this carbon dioxide must therefore be dissolved in the ocean.
On this basis, Trumbo and Brown drew some general conclusions about the state of Europa’s ocean. They suggest that the ocean is highly oxidized, which is consistent with models depicting the downwards motion through the ice of oxidants such as molecular oxygen and hydrogen peroxide that formed in the radiation environment on the surface. However, even NIRSpec’s powerful eye could not determine whether the carbon dioxide came from living organisms. “More measurements and higher accuracies will be needed to further establish the formation and evolution processes of the observed carbon on Europa,” Villanueva agrees.
Something else that will require more measurements is the plumes of water spraying high above Europa’s surface. Although the Hubble Space Telescope detected such plumes on three occasions over the past 10 years, the JWST saw none during its observations in November 2022. While this doesn’t mean the plumes aren’t real, it does place an upper limit of 300 kilograms per second on the mean rate of material spewing out. It also means that the plumes, if they exist, must be intermittent.
Further information is likely to arrive within the next decade, with the European Space Agency’s Jupiter Icy Moons Explorer (JUICE) due to perform two fly-bys of Europa once it arrives in the Jovian system in 2031. NASA’s Europa Clipper mission is also due to set sail for Jupiter in 2024, with a planned arrival date in 2030. The JWST’s observations will play a vital role in determining where, and what, the two missions should study on Europa’s surface.
Quantum fabrication Element Six is applying its patented technology and know-how in PECVD fabrication to produce, at scale, quantum grades of single-crystal diamond for quantum networking applications. (Courtesy: Element Six)
While today’s fibre-optic networks distribute classical information across global length scales, the quantum networks of the not-so-distant tomorrow will exploit the exotic properties of entanglement and superposition to securely transmit quantum information between end-users at the same global scale. This capability will enable quantum-encrypted communications for all manner of organizations – from governments and banks to healthcare providers and the military – and open the way, inevitably, to the implementation of at-scale parallel quantum computing resources, with remote computing nodes linked quantum mechanically across the network.
Though still under development, quantum repeaters represent a core enabling technology as the quantum internet comes into view, serving a similar function as fibre amplifiers in classical optical networks by correcting for the loss and infidelity that occur as quantum information propagates over long distances (though without disrupting the quantum state of light as it passes through the network).
Quantum repeaters operate by transferring information encoded on photons onto a stationary memory qubit where the information can be stored and corrected. Defect qubits, such as colour centres in synthetic diamond, are shaping up as credible candidates for this task because they have an effective interface with light (the source of their colour) and because these defects can have a long-lived “spin” memory. Two classes of diamond-defect qubits are the focus of intense R&D interest in this regard: the nitrogen-vacancy spin centre (NV) and the silicon-vacancy spin centre (SiV), both of which are formed by removing two adjacent carbon atoms from a synthetic diamond crystal lattice and replacing them with a single nitrogen or silicon atom, respectively.
Bart Machielse “In collaboration with Element Six, AWS is seeking to understand what the factors are that make synthetic diamond quantum-grade.” (Courtesy: AWS)
Here Bart Machielse, senior quantum research scientist at the AWS Center for Quantum Networking, tells Physics World how his team is accessing the leading-edge materials science and fabrication capabilities of research partner Element Six to realize “quantum advantage” in optical communications systems using synthetic diamond.
What’s the headline goal for the AWS quantum networking programme?
The AWS Center for Quantum Networking is located in Boston, Massachusetts, and has all the tools needed to support an independent R&D initiative in quantum communications. As such, we fabricate, test, characterize and optimize our own devices for proof-of-concept testing in long-distance quantum networking experiments. In my role, I lead the devices and packaging team with a remit to drive the scale-up and integration of quantum photonics (including synthetic diamond photonics) in high-grade research demonstrators of deployment-grade quantum networking technologies.
Presumably, collaboration is a given in such a competitive field?
It’s mandatory. We rely on R&D partners who can bring unique technical capabilities, deep domain knowledge and specialist know-how to the table. Our collaboration with Element Six, for example, is all about reimagining and transforming synthetic diamond as a material platform for photonic devices destined for applications in quantum memories and quantum repeaters. In brief, that means progressing from where we are now – a substrate that’s finnicky to work with when it comes to nanophotonic fabrication – to a material that’s compatible with scalable, reproducible and cost-effective semiconductor-style manufacturing.
How does the collaboration with Element Six work operationally?
Working with Element Six is a true R&D collaboration. For starters, there’s tight integration between the materials experts at Element Six and the quantum photonics team here at AWS. The collective conversation is key to successful translation of the baseline materials know-how at Element Six into enhanced device-level performance.
It’s all about the pipeline in this regard: our job at AWS is to take the diamond substrates that Element Six produces and apply our specialist optical, fabrication, microwave and cryogenic tools to better understand the quantum performance of that material when it’s being fabricated into photonic devices – in particular, how the optical emission maps versus fundamental materials properties such as dislocation density, strain, surface smoothness and the like.
What are the main manufacturing and engineering challenges when it comes to deploying synthetic diamond in quantum networking systems?
Right now, a lot of what we do in synthetic diamond photonics is highly probabilistic – for example, in terms of sample purity, the formation of defects, the exact location of those defects and the macro-scale crystal properties of the substrate material. In short, there is a lot of understanding needed to link the properties required for the application to the material specifications so that it can be fully scaled. In collaboration with Element Six, AWS is seeking to understand what the factors are that make synthetic diamond quantum-grade; also what the limits are when it comes to driving down the cost/complexity of materials processing so that you get what you need, not what you don’t need.
Optical building blocks A quantum memory chip built by the AWS Center for Quantum Networking. The assembly above uses synthetic diamond from Element Six and is part of a prototype quantum repeater. (Courtesy: AWS)
One thing is certain: Element Six’s commitment to ongoing investment in plasma-enhanced chemical vapour deposition (PECVD) growth techniques will be critical to the design, development and at-scale fabrication of diamond devices for quantum networking applications. The priorities are already clear: improving control over the types of defects created and the material incorporated during synthetic diamond growth; widening the different morphologies of diamonds that can be produced at scale; and simultaneously reducing the cost of manufacturing.
So put another way: materials innovation is nothing without control?
That’s correct. The task going forward is to remove all the variabilities from the synthetic diamond fabrication process so that we can optimize the design, integration and performance of quantum photonic devices and subsystems out in the network. Even more fundamental: when we fabricate a synthetic diamond photonic device today, we use the top few microns of a 0.5 mm thick diamond, so we need to find ways to be a lot more efficient. Think manufacturability, think cost reduction and, ultimately, synthetic diamond substrates that are more “fabbable” – i.e. compatible with standard semiconductor fabrication techniques.
What does the AWS technology roadmap look like in quantum networking?
In time, it should be possible to deploy, in volume, diamond photonic devices containing quantum memories that serve as quantum repeaters – essential building blocks for what we’re calling “entanglement distribution networks”. Near term, the R&D priority is to work with companies like Element Six to deliver the quantum-grade synthetic diamond substrates that will make the device-level engineering and systems integration more reliable, scalable and network-ready. Our hope is that advances in synthetic diamond fabrication will, sooner rather than later, yield downstream technology innovations that make AWS quantum communication systems a must-have tool in the network security and privacy arsenal of our corporate customers.
The search for a quantum ‘game-changer’
Quantum-grade synthetic diamond is being lined up for a whole new range of photonic applications in quantum computing, quantum metrology and quantum networking – many of which have no analogues in existing materials. The academic community, for its part, is focused on pushing the limits of what can be done with this material, leading to paradigm shifts in quantum performance, while industry is all about taking the current state-of-the-art and figuring out how best to package and integrate engineered synthetic diamond into next-generation quantum devices.
With translation from research lab to the market now front-and-centre, the measures of success for quantum diamond devices are increasingly defined along coordinates like reliability, robustness, manufacturability, scalability and cost/performance ratio. That shift in mindset and priority informs the work of the quantum development team at Element Six, which is applying its patented technology and know-how in PECVD fabrication to produce, at scale, quantum grades of single-crystal diamond containing controlled levels of NV and SiV spin centres for applications in quantum networking systems and beyond.
Daniel Twitchen“It’s exciting to be pooling our expertise in synthetic diamond with AWS’s know-how in photonics.” (Courtesy: Element Six)
“Synthetic diamond can offer game-changing solutions and allow our customers and partners to do something that couldn’t be done before – from building a laser with unprecedented power densities to a synthetic diamond ‘acoustic dome’ with exceptionally high frequency characteristics,” explains Daniel Twitchen, chief technologist at Element Six.
“Bart Machielse and his team at AWS are a case in point,” he adds. “They came to us because, over the years, we have developed a large toolbox of synthetic diamond innovation capabilities. Our accumulated know-how aligns with the technical challenges that must be solved to realize a diamond quantum networking platform, plus we have demonstrated the ability to scale synthetic diamond into a production environment.”
At the same time, Element Six realizes that new growth markets for synthetic diamond will require solutions that make it easier for the material to be used – within the emerging quantum supply chain and elsewhere. “Ultimately, the need and opportunity lie not just in making quantum-grade synthetic diamond, but processing and integrating it within photonic devices,” notes Twitchen. “And, in so doing, reducing the barriers for adoption of synthetic diamond.”
Right now, the focus for Twitchen and his Element Six colleagues is to scale the company’s industrial partnerships in the field of quantum networking, having already established the potential of synthetic diamond in academic collaborations with leading quantum networking groups at TU Delft in the Netherlands as well as MIT and Harvard University in the US.
“What’s been missing to date,” concludes Twitchen, “is a big industry player saying it can roll out quantum communications systems by introducing a new generation of quantum-secure network services for their customers. They don’t come much bigger than AWS, so it’s exciting to be pooling our expertise in quantum-grade diamond with AWS’s know-how in photonics to make this vision a reality.”
High-temperature superconductivity hit the headlines in spectacular fashion this year following a series of results that supposedly reached a “holy grail” of condensed-matter research. We had a “summer of speculation” over the material LK-99 in which a team of researchers in South Korea claimed that a modified form of lead apatite could conduct electricity without resistance at ambient pressure and temperatures. In the end it took other researchers barely a few weeks to establish that LK-99 was not a room-temperature superconductor at ambient pressure after all. But that still leaves the controversial claims made a few months earlier by Ranga Dias at the University of Rochester and colleagues of near-ambient superconductivity in nitrogen-doped lutetium hydride unresolved.
The saga began in October 2020 when Dias and his team published a paper in Nature (586 373), in which they claimed to have discovered superconductivity at a balmy 15 °C in a hydrogen sulphide material under high pressure. Concerns were, however, soon raised over that finding, which led to rebuttals and counter rebuttals in peer-reviewed publications and on the arXiv preprint server that sometimes verged on the unprofessional. There have even been suggestions that “cease and desist” letters were sent by lawyers to arXiv and to rival scientists. Following concerns with the hydrogen sulphide paper, it was retracted in September 2022 by editors at Nature (though Dias and colleagues maintain that they stand by their work).
The fate of the recent lutetium hydride paper, also published in Nature (615 244), is unknown. Strangely, the paper has an unusual ethics declaration that revokes open access to the information required to reproduce the authors’ exact steps. Although the raw data files have been made publicly available from Dias, arXiv has been inundated with reports from researchers who have failed to reproduce the room-temperature superconductivity with their own samples. Some months later, however, a team led by Russell Hemley from the University of Illinois claimed to have observed evidence for near ambient superconductivity in a sample provided by Dias.
Complex situation
Criticism and scepticism are, of course, vital for the progression of science. But to have scientists publicly express their distrust in other scientists harms the very trust we need from the public to fund scientific work. Such criticism also distracts researchers from making legitimate discoveries as they spend their time replicating or analysing what could be bogus results. As an early-career physicist myself, navigating this minefield is complex. So, how can we prove negligence from people in positions of influence who use their status to continue to attract funding for their university or institute? Where do we go if we have concerns about academic integrity? How can we report our concerns to the community when it takes months to pass through peer review?
I recently posed these issues to physicists at the final session of the Gordon Conference on Superconductivity, which was held in Les Diablerets in Switzerland from 30 April to 5 May. My questions, however, were met with what seemed like a wall of stunned silence. Hands eventually rose and people pointed out that there is no good scientific platform to challenge research that one has question marks about. Some researchers have had conversations on Reddit or PubPeer – a website allowing for anonymous comments on scientific papers – but this may not be considered an avenue for serious scientific discourse. Nature has a “comments” section below the HTML version of an article, but comments are seemingly left unaddressed by editors.
A precarious option is to file a formal case of academic misconduct with journal editors or with the institutes where the researchers are based. But this carries enormous risks
As for arXiv, it is a vital source of information, providing rapid publication of non-peer-reviewed preprints. But its focus is simply on providing a platform for new and original research. While comments are not uncommon, the arXiv website is not geared up for open debate or for people to raise concerns – and those who do could end up being barred by the site’s moderators. Of course, it is possible to raise concerns in a formal paper submitted to a peer-reviewed journal but that can be tricky. Peer review can take months (whereas concerns require immediate action) while finding the correct journal to host a rebuttal is not simple. The original journal where contentious work appeared may not want to court controversy, while a rival journal will simply not want to get involved in another publication’s affairs.
An even more precarious option is to file a formal case of academic misconduct with journal editors or with the institutes where the researchers are based. But this carries enormous risks. For a junior researcher still making their name in science, it could cost them their career. For a senior researcher, it could damage a well-established reputation. Journals will, of course, defend their decision to publish highly citable articles while research institutes will want to defend their employees. Turning a blind eye merely lets perpetrators carry on getting funded, protected by their employers.
These issues must be addressed. Editors of journals need to check the credibility of authors before publishing a high-profile result that may get attention from the world’s media. Research institutes need to undertake an unbiased, open and thorough investigation following allegations of misconduct. Scientists, meanwhile, have to keep discussions professional while reporting suspected foul play and not fear repercussions should they do so.
The current situation in hydride superconductivity has no simple solution. It is made more complex given that Dias has submitted a patent on a lutetium hydride material that is apparently a room-temperature superconductor at ambient pressure. Yet we must find something that works if trust in science is to be maintained. Although science can be fraught with tension and competition, we are a single community and we must all collaborate to preserve our standards of research and academic integrity.
A technique for harvesting low-speed wind energy using anchored ionic droplets has been developed by researchers in China and the UK. The approach – which taps into winds that are too weak to drive a turbine – could be used to power small electronic devices.
Wind power has seen explosive growth in recent decades as the world turns from fossil fuels to renewable sources of electricity. Between 2001 and 2021, the estimated global wind power capacity increased from 24 to 840 gigawatts.
Due to technical limitations, however, these installations all require the wind to exceed a certain minimum speed. The reason for this is that the power output of a turbine is proportional to the cube of the wind velocity. Thus, a decrease in wind speed results in a dramatic decline in energy production as the blades cannot rotate effectively and the turbine become unreliable.
In practice, these restrictions mean that wind farms can only operate in specific geographies – either wide open land, or offshore – and need regular all-year-round wind speeds of at least 5 metres per second to perform well. Unfortunately, geographies that do not meet these criteria (including forests and cities, where trees and buildings obstruct wind flow) are far more abundant and widely distributed than their optimal counterparts.
Harvesting the wind
To address this limitation, a team led by inorganic chemist Shan Peng of China’s Hebei University developed a novel system capable of translating low-grade wind into electricity even when the wind speed drops as low as 0.2 metres per second. The team’s approach is based on previous studies showing that energy can be harvested from the movement of raindrops on a surface by redistributing charge around the interface between droplet and surface. The new solution, however, involves drops of an ionic liquid, 3-Methyl-1-octylimidazolium chloride, that are partially fixed in place by a special substrate sporting an array of nanowires made from a silicone-based polymer, polydimethylsiloxane.
As low-speed wind blows over each anchored droplet, it causes a circulating flow within that redistributes the surface charge across the liquid. This surface charge can then be tapped into using a pair of electrodes placed under the centre and edge of the droplet. When the wind blows in different directions, the team demonstrated that different patterns of flow circulation arise within the ionic liquid droplets.
Writing in PNAS, the team report that such stratified circulating flow within a single drop can generate a voltage output of up to ~0.84 V. Using “wind farms” containing many drops, the team managed to scale up the output to about 60 V. They also demonstrated that this small-scale droplet-based wind farm could have practical applications by using it to produce enough electricity to power the screen of a pocket calculator.
“Given the widespread distribution and easy accessibility of low-grade wind, these findings expand the great potential of currently untapped low-speed wind as an attractive energy resource for powering electronics, such as LCD screens,” they write.
Untapped potential
With their initial study complete, the researchers are now looking to upgrade their anchored droplet design to fine-tune the intermolecular interactions between the ionic liquid and the supporting base. They hope this will enhance the flow-directed redistribution of anions and cations and thereby improve the design’s capacity for power generation.
According to Patrick James, a physicist and energy specialist at the University of Southampton, UK who was not involved in the present study, the benefits of the new design are likely to be limited to niche applications. “Obviously these are very low wind speeds and wind speed cubed is the key issue here,” he tells Physics World. “The paper talks about a future application of very low power applications so I think a review needs to be clear about this aspect.”
