Page 241 – Physics World

Home » Page 241

Graphene ribbons advance twistronics

Ribbons of graphene, rather than squares, could make a better platform for probing the unusual electronic effects that arise from twisting and straining adjacent layers of two-dimensional (2D) materials. This is the finding of scientists in the US, Denmark, France and Japan, whose approach differs significantly from previous “twistronics” studies that focused on twisting two flakes of material with respect to each other and then stacking them. According to the team, the new ribbon-based technique could give researchers better control over the twist angle, making the electronic effects easier to study.

In recent years, researchers have found that they can change the electronic properties of 2D materials by stacking layers of these materials atop each other and varying the angle between them. For instance, a bilayer of graphene does not normally have a band gap, but it develops one when placed in contact with another 2D material, hexagonal boron nitride (hBN).

This change occurs because the lattice constant of hBN – a measure of how its atoms are arranged – is nearly the same as that of graphene, but not quite. The slightly mismatched layers of graphene and hBN form a larger structure known as a moiré superlattice, and the interactions between nearby atoms in this superlattice allow a band gap to form. If the layers are then twisted so that they are further misaligned and the angle between them becomes large, the band gap disappears. Similarly, graphene on its own can be tuned from semi-metallic to semiconducting and even superconducting depending on the angle between the individual graphene layers.

To achieve this variety of electronic properties in conventional materials, scientists normally need to change their chemical composition by introducing dopants, or deliberate impurities. Being able to do this in a 2D material simply by altering the twist angle between layers is therefore a fundamentally new direction in device engineering, and has been dubbed “twistronics”.

The problem is that twist angles and the associated strain are hard to control, meaning that different areas of a sample may have inconveniently different electronic properties. In the latest work, a team led by Cory Dean of Columbia University in the US overcame this problem by placing a ribbon-shaped graphene layer (rather than a square flake as is usually the case) atop a layer of hBN and slowly bending one end of the ribbon using a piezo-atomic force microscope. The resulting structure has a twist angle that varies continuously from the point at which the ribbon starts bending all the way through to its end. And instead of uncontrolled variations in strain, the sample now has a uniform strain profile that can be fully predicted by the boundary shape of the bent ribbon.

Maintaining angle and strain gradients

In their experiments, which are detailed in Science, Dean and colleagues bent one of the graphene layers into a shape that resembles a semi-circular arch. Then they placed this layer on top of a second, unbent, layer. “When placed together in this manner we intentionally introduce an angle gradient along the arc, and a strain gradient across the arc,” Dean explains. “We find that instead of allowing for random fluctuations in the local twist angle or strain, the combined two layers maintain the angle and strain gradients that we impart during the bending process.”

Bending the graphene ribbon is not easy, however. The researchers managed it by first cutting a ribbon from a larger piece of graphene using an atomic force microscopy (AFM)-based process. Next, they fabricated a separate “slider” from a multi-layer, bulk piece of graphite consisting of a round disc fabricated with handles on the outer rim. This slider was then positioned onto one end of the ribbon and pushed across it using the end of an AFM tip. “The slider can be controlled by the AFM tip and removed after the ribbon has been bent into shape,” explains Dean.

A key feature of this process is that the graphene ribbon’ interfacial friction is relatively low when placed on hBN, meaning it can be bent under load, yet high enough to allow the ribbon to hold its bent shape when the load is released.

The extent to which the ribbon will bend depends on the length and width of the ribbon and how much force is applied to the end of it by the AFM tip. The researchers found that long, narrow ribbons (that is, ribbons with a large aspect ratio) are the easiest to bend in a controlled way.

“Unprecedented access to the twisted angle phase diagram”

Being able to continuously tune both strain and twist angle will give researchers unprecedented access to the “phase diagram” of twisted angles, Dean tells Physics World. “The electronic band structure of twisted bilayer is extremely sensitive to twist angle, with, for example, the ‘magic angle’ being defined with only one tenth of a degree of 1.1°. Slow and controllable twisting means we can map this dependence in a single device to a precision not previously possible.”

Making graphene nanoribbons stable

And that is not all: since the role of strain on the magic angle bilayer graphene systems is almost totally unknown experimentally, the new technique provides the first opportunity to measure it in a reproducible way. “Technically, the notion that introducing a strain gradient could help to suppress random twist angle variations was an unexpected surprise for us,” Dean says. “This opens up interesting ideas on how to interplay strain engineering and spatially-controlled angle variations to gain further control over the electronic band structure in twisted layer systems.”

The Columbia team is now mapping the strain-angle phase diagram around the magic angle range in twisted bilayer graphene using a combination of transport- and scan-probe spectroscopy. The researchers are also exploring whether they can apply the technique to other 2D materials systems. In semiconductors, for example, bending could guide and funnel excitons (electron-hole pairs), while in magnetic 2D systems, it might be used to create unusual magnetic textures. “Finally, we are exploring ways to achieve bending through electrostatic or other non-mechanical means,” Dean reveals. “These could allow for in-situ dynamic control of the twist angle in bilayer systems.”

Polarized dust reveals strong magnetic field of ancient galaxy

The most distant galactic magnetic field ever observed has been reported by an international team of astronomers. The field belonged to a galaxy called 9io9, which we see as it was about 11 billion years ago – about 2.5 billion years after the universe was created in the Big Bang. The discovery was made by studying radiation emitted by dust grains that were aligned by the galaxy’s magnetic field.

Magnetic fields have long been known to play a key role in the formation of stars and galaxies. However, large-scale ordered magnetic fields have only been observed in the Milky Way and nearby galaxies.

While there has been some theoretical work on the subject, it had not been known how rapidly magnetic fields could form around young galaxies and hence play a role in their future evolution.

Poorly understood

“Magnetic fields are one of those things that are key components in galaxies but that are relatively poorly understood, compared to other processes involved,” explains James Geach, from the University of Hertfordshire, who is the lead author of a paper in Nature that describes the discovery.

One reason for this poor understanding is that detecting distant magnetic fields in young galaxies is a technical challenge. As a result, magnetic fields have often being absent in many models and simulations of galaxy formation and evolution. “There was a chance that the field may be very faint, and we may not be able to detect it,” Geach explains.

The scientists chose to study 9io9 because it is a particularly luminous galaxy that is gravitationally lensed. This lensing occurs when a massive object, like a black hole or a galaxy cluster, bends light from the galaxy that passes nearby. This can have the effect of magnifying the galaxy as it is seen on Earth.

Compass needles

Using the Atacama Large Millimeter/Submillimeter Array (ALMA) in Chile, the team detected thermal emissions from dust grains around 9io9. Dust grains are not perfectly spherical, so they can align to a magnetic field like compass needles. These grains can absorb electromagnetic radiation and re-emit it at longer wavelengths

If the dust grains are magnetically aligned, they will emit polarized light. By analysing the degree and orientation of this polarization, the team could infer the direction and strength of the magnetic field in the region where the dust grains were located. They found that 9io9’s field strength is about 20 times that of the Milky Way and extends about 16,000 light–years across . The team used these data to create a magnetic field map of the distant galaxy.

“This is showing that even within a relatively limited time span from the Big Bang, magnetic fields like the ones we see in more local galaxies can be established,” explains Geach.

Rainer Beck is an expert on galactic magnetic fields, who retired from the Max-Planck Institute for Radioastronomy in 2018. He told Physics World that he was surprised by 9io9’s field strength: “It is really amazing, and it’s something that says that magnetic forces are already very, very important in the very early universe”.

Peering back in time

Beck adds that that 9io9 represents an “enormous jump” in our understanding of the magnetic fields of older galaxies. “Until now, we’ve only had some indication of ordered fields up to a redshift of 0.4, but this is a redshift of 2.6.”

Redshift refers to the degree to which the wavelength of light from the galaxy has been stretched by the ongoing expansion of the universe – with higher redshifts corresponding to older and more distant objects.

As observed, galaxy 9io9 is a still in its infancy and is located in the early universe. As a result, it is still rich in turbulent ionized gases that have not collapsed to form stars, and the researchers have developed a theory about how this turbulence is related the magnetic field.

Turbulent motion

The galaxy is shaped like a disc that rotates rapidly. It also contains turbulent motion from stellar feedback, which refers to the physical processes of stars that can shape their environment. This includes stellar winds, which are jets of charged particles that shoot out of stars.

“We think that it’s that intense star formation that’s churning up the gas that has initially amplified the magnetic field,” said Geach, “You have the rotation of the galaxy happening at the same time, which is sort of winding up the field into a more coherent structure.”

The team suggests that this “dual dynamo” may be how galactic-scale ordered magnetic fields can form early in young galaxies.

Geach says that future studies can aim to map the magnetic field in higher resolution to resolve the different components of the field and reveal its fine structure.

Female PhD students miss out on chance to become inventors, finds study

Women in technical PhD programmes are given less hands-on experience in patenting and commercial science compared to their male counterparts. That is according to a new study by researchers in Demark and the US, which finds that this lack of experience results in fewer women becoming inventors. The team say the findings have implications for diversity and inclusion in academia as well as in startups and larger firms (Proc. Natl. Acad. Sci. 120 e2200684120).

The study was carried out by Mercedes Delgado from Copenhagen Business School and Fiona Murray from the Massachusetts Institute of Technology, who examined data on PhD students trained at the top 25 US universities — as ranked by patent counts — between 1995 and 2015. They found that, overall, 4% of PhD candidates file a patent as a result of their studies. Yet while women make up about 30% of PhD students at the 25 universities, they only made up 20.7% of new inventor PhDs. This inventor gender deficit occurs even among students working in the same lab on similar topics under the same advisors.

According to the researchers, the difference between genders could be because supervisors who publish many patents tend to serve as a catalyst for students to also become adept at patenting – but those supervisors tend to opt for male students. “Female PhDs have a 21% lower likelihood of [working] with advisors who are top inventors than male PhDs — and even when [they do they] are 17% less likely than their male PhD counterparts to become new inventors,” says Murray.

Early intervention

Alongside this “leaky pipeline”, other factors identified for the gender split include male and female students having different levels of access to resources and self-assessment of skills. Another factor, according to the researchers, is that “women’s innovation skills and contributions are somewhat under-valued by advisors”.

The team propose several steps to reverse the trend. One would be to refine the advisor–advisee matching process to place more women with doctoral supervisors who are themselves established inventors. Another is to support women already in faculty positions to engage in high levels of patenting, thereby increasing the pool of women inventors who can serve as doctoral advisors.

The researchers now plan to explore the effectiveness of some of their proposed interventions, alongside quantifying the long-term impacts of having — or not having — an early training in patenting and commercial science. “Imagine you became a new inventor during your PhD studies,” adds Delgado. “We think this can have a long-lasting effect, because after graduation you enter an organization and already know how to do commercial science — so you’ll be an even more productive inventor during your career.”

Materials science: the rule of three that guides its development

“To paraphrase Shakespeare,” Daniel Ucko told me, “some periodicals are born as materials science journals, some achieve it, and some have materials science thrust upon them.”

Ucko is well placed to observe the changing face of materials science, having originally done a PhD in condensed-matter physics at University College London before spending almost two decades as an editor at Physical Review Letters over at the American Physical Society (APS). While at the APS Ucko also did a PhD in philosophy at Stony Brook University – where I was his supervisor – and earlier this year he became the society’s first head of ethics and research integrity.

Ucko articulated the above principle, which I call the “rule of three”, in an article in the latest book from World Scientific on the history of materials science. Edited by me and due out next year, the book is called Between Science and Industry: Institutions in the History of Materials Research. It conceives of institutions as not just physical laboratories, but as the organizational, educational and regulatory structures needed to carry out research. This overarching structure helps the general reader to understand materials research without much background.

The book follows on from two earlier volumes. The first – Between Making and Knowing – was edited by historians Joseph Martin and Cyrus Mody and covers nearly 50 tools and techniques, ranging from simulations and centrifuges to neutron and synchrotron light sources. The second volume – Between Nature and Society – was edited by the philosopher and historian of science Bernadette Bensaude-Vincent and provides the “life stories” of 15 materials, including cement, glass, plastics, rubber and rare earths.

Ucko’s article in volume three, where he makes his Shakespearean reference, examines journals that morphed, for example, from metallurgy to materials science. It looks at journals that spun off from other journals as well as journals that were born as materials-only publications. It also discusses the vast scope of journals, which range from those dedicated to one small sub-field to publications with a broad appeal. There are even materials-science journals that don’t have the word “materials” in their name.

As Ucko’s article reminds us, the topic of materials-science journals is far more complex than it appears, for they play a mediate role. “A journal can only exist if there is a community that wants what it contains,” Ucko told me. “But it’s also building a community through the diversity of articles that it presents. What’s more, communities keep moving, and journals have to keep moving with that.”

It’s all in the name

One way a journal shapes the community it serves is by how it bills itself, which may differ from its actual content. “Look at the launch editorial,” Ucko said. “The editorial in the first issue tells you how it wants to present itself – how it wants to leap into the scene.” Sometimes a publication, such as the Journal of the American Chemical Society, publishes much materials science but does not talk about itself in those terms. Other journals, such as Nature Materials, are explicit about their scope.

One way a journal shapes the community it serves is by how it bills itself, which may differ from its actual content

Some journals have found a need to change direction into materials science, but had to take time to move in the new direction. Take Acta Materialia. Born in 1953 as Acta Metallurgica, it was renamed Acta Metallurgica et Materialia in 1990, and then became Acta Materalia in 1996. “But it’s not like the journal suddenly changed direction, throwing open its doors to a new diversity,” Ucko pointed out. The contents of the first issues after the name changes were still primarily about metallurgy and alloys.

Linn Hobbs, a retired physicist who was formerly at the Massachusetts Institute of Technology, wrote an entry in the book on materials-science societies. Much of the dynamic that Ucko describes for journals is also evident here. Professional societies are mediators too, helping researchers to do their work and making them realize why it’s worth it. Societies and journals, Hobbs writes, not only make researchers want to “talk the same language” but also provide the forum in which it takes place.

Just as materials-science journals have changed, so too have professional materials-science societies. As Hobbs notes, some of them, such as the Materials Research Society, started out that way while others morphed into the field. But professional materials-science societies are unusual, he notes. Compared with, say, physics or chemistry they tend to be more interdisciplinary and they co-ordinate a broader range of scientific, commercial and industrial interests.

The critical point

So why the rule of three? I see it as about how materials science abruptly became a discipline in its own right in the late 1950s. One was the development of instruments, in particular electron microscopes, that could be used to study previously distinct materials, such as glasses, metals or ceramics. Another factor was the post-Sputnik demand for materials suitable for use in missiles. Yet another was the progressive unification of previously separated areas by the theory of defects and dislocations.

The confluence of these factors quickly made it unthinkable not to teach – and organize institutional support – for materials science as a unified field. Most of the articles in Between Science and Industry focus on institutions in the second half of the 20th century, after materials science began to warrant specialized institutions. But with the development of biomaterials, nanomaterials, and 2D and quantum materials, as well as the blending of the border between “hard” and “soft” materials, who knows where the field will go next?

Plastic scintillation detectors prove a win-win in clinical physics research and education

Disruptive innovation, customer collaboration, clinical translation: these are the strategic reference points underpinning the product development roadmap at Medscint, a Québec City-based technology company that combines expertise in photonics, scintillation dosimetry and medical physics. The end-game: nothing less than a paradigm shift in radiotherapy dosimetry best practice enabled by a new generation of plastic scintillators that combine near-water-equivalence and real-time response with high spatial resolution and MR-Linac compatibility. Medscint’s optical detectors – known commercially as the HYPERSCINT Research Platform – also offer multipoint capability with a compact footprint (0.5 mm long, 0.5 mm diameter), which makes them ideal for small-field dosimetry and advanced phantom development.

“Our proprietary know-how in optical science and plastic scintillators comes into its own as radiotherapy treatment fields get smaller and geometrically more complex,” claims Jonathan Turcotte, co-founder and chief marketing officer at Medscint. With no need for small-field correction factors to characterize device behaviour, Medscint dosimeters provide a real-time measurement tool that combines high linearity with respect to dose and dose rate. That wide linear dynamic range is relevant at both ends of the treatment spectrum, whether for novel low-dose-rate irradiation schemes or – with bespoke functionality for linac pulse counting and dose-per-pulse measurement – as an adjunct to ultrahigh-dose-rate FLASH radiotherapy applications (which have the potential to drastically reduce collateral damage and toxicity in normal healthy tissue while preserving anti-tumour activity).

Out of the lab, into the clinic

While clinical translation is the commercial priority over the near and medium term, Turcotte and his colleagues have to date positioned the HYPERSCINT Research Platform with a cohort of innovative, cross-disciplinary R&D teams working to realize next-generation radiotherapy systems. “As an early-stage technology company,” he explains, “we have a collaborative relationship with our customers and research partners – a total of 25 groups across North America, Europe and Asia who help to shape our product development and, ultimately, inform the path to at-scale clinical translation.”

Mark Foley “We have set up a dedicated research stream to evaluate and benchmark Medscint’s plastic scintillation detectors.” (Courtesy: University of Galway)

A case study in this regard is Mark Foley and his team in the medical physics research cluster at the University of Galway in the west of Ireland. Foley’s broad-scope research interests centre around enhanced radiotherapy schemes, with pioneering work on Monte Carlo modelling and simulation as well as next-generation scintillation dosimetry systems. His research programme dovetails with a busy teaching load, spanning undergraduate courses in biomedical and radiation physics as well as Galway’s MSc in Medical Physics, the first master’s programme in Europe to receive formal accreditation from the North American Commission on Accreditation of Medical Physics Education Programs (CAMPEP).

“We became Medscint’s first European customer when we purchased the HYPERSCINT Research Platform back in summer 2021,” explains Foley. The system has since been put through its paces in a series of five pilot projects involving MSc and PhD students within the Galway medical physics cluster – though the related research activity is set to scale sooner than later. “We have set up a dedicated research stream to evaluate and benchmark Medscint’s plastic scintillation detectors,” says Foley. “This R&D effort sits alongside an established work programme where we’re developing a new class of inorganic scintillation detectors for advanced dosimetry applications.”

After his medical physics students are up to speed with the HYPERSCINT Research Platform, Foley encourages them to pursue further specialist learning and know-how in scintillation dosimetry – chiefly through short-term research placements at partner laboratories within Galway’s international network. “We’re setting our MSc and PhD students up with the skills and technical domain knowledge they need to hit the ground running,” explains Foley. “We want to make sure there’s no prohibitively steep learning curve when they begin their research projects.”

One established collaboration in this regard is with Magdalena Bazalova-Carter’s XCITE Lab at the University of Victoria in British Columbia, Canada. The XCITE team is an early-adopter of Medscint’s real-time, small-field dosimetry solution for research studies on FLASH irradiation schemes in very-small-animal experiments – exposing fruit fly larvae, for example, to ultrahigh dose rates and tracking comparative survival versus conventional irradiation schemes. The lab is also evaluating the FLASH effect on healthy tissue in mice.

Such collaborations, it seems, represent a win-win. A case in point is Kevin Byrne, a former MSc student in Foley’s group who, following a research placement at XCITE, is now working as a research medical physicist within the division of translational radiation sciences at the University of Maryland School of Medicine (Baltimore, MD). Under the supervision of Kai Jiang, assistant professor of radiation oncology, Byrne continues to work on plastic and inorganic scintillation detectors within a wider research programme investigating the FLASH effects of ultrahigh-dose-rate electron and proton beams on preclinical models. “There’s something of a ‘virtuous circle’ in play here,” explains Foley, “with Kevin progressing to supervise other visiting MSc and PhD students from Galway with their projects in scintillation dosimetry.”

Creative education

Notwithstanding Galway’s exploitation of Medscint technology in a medical physics research context, Foley is also putting the HYPERSCINT Research Platform front-and-centre within his undergraduate teaching. “The task is to create a more dynamic research-led learning environment by exploiting portable demonstration devices like the Medscint system,” he explains. “In this way, we’re using Medscint’s plastic scintillation detectors to introduce the fundamentals of radiation dosimetry to first-year students, while reinforcing those concepts with a structured learning path all the way through the syllabus to fourth-year undergraduate level and master’s studies.”

At the same time, argues Foley, the status of Galway’s MSc in Medical Physics is further enhanced by CAMPEP accreditation, which means master’s students graduate with “inherent transferability and mobility” as part of the academic package. “You’ll find our MSc students entering research and clinical physics roles at leading radiation oncology centres in the UK and Ireland as well as North America, Australia and New Zealand,” he concludes. “Another big plus of CAMPEP compliance is that it eases the path when we’re establishing new collaborations with other CAMPEP-accredited research programmes in the US and Canada.”

Disruptive innovation, clinical translation

**Jonathan Turcotte** “Plastic scintillators represent a disruptive technology in radiotherapy QA and dosimetry.” (Courtesy: Medscint)

Medscint aims to “rewrite the rulebook on small-field dosimetry” based on its proprietary optical know-how in the field of plastic scintillation detectors. That’s the claim of Jonathan Turcotte, the vendor’s co-founder and chief marketing officer, whose focus, along with that of his colleagues, is shifting inexorably to the fine detail of clinical translation and the QA requirements of clinical end-users for next-generation radiotherapy modalities.

“We’ve built up the business so far by gaining traction with a cohort of innovative, research-led medical physics programmes – all of them working to define tomorrow’s best practice in radiotherapy dosimetry,” he explains. “The next step in Medscint’s evolution will be more of a twin-track strategy – continuing to target the leading-edge research customers while pivoting in the near term to the clinical QA market.”

Later this year, for example, Turcotte and his team expect to secure 510(k) regulatory approval from the US Food and Drug Administration (FDA) for a clinical system that’s being lined up for small-field dosimetry applications in machine QA. The subsequent CE mark is slated for 2024 as a precursor to installations with clinical customers in the European Economic Area (EEA).

“While plastic scintillators represent a disruptive technology in radiotherapy QA and dosimetry,” notes Turcotte, “it’s significant that roughly one in six clinical physics programmes with CAMPEP accreditation are already working with our products in a research setting.”

Multidisciplinary collaboration opens the way to strategic innovation in wireless technology

Lancaster University physics graduate Ben is a member of the Wireless Products team at BAE Systems Digital Intelligence, a company that employs more than 4500 digital, cyber and intelligence experts to help government, military and commercial customers defend against advanced threats. He talked to Physics World about the joys of working at the cutting edge in electronics and digital signal processing while applying his mathematics and physics skills to diverse engineering problems.

What’s it like to work in the Wireless Products team?

On my first day in the office, I vividly remember being so happy to see colleagues writing equations, drawing diagrams and elaborating elegant technical explanations on whiteboards – reminiscent of working in the library meeting rooms at Lancaster during my physics degree. Overhearing staff discussing their R&D projects meant learning about exciting scientific and engineering concepts of which I knew very little – plus, like my colleagues, I still try to find any excuse to work things out on a whiteboard.

By extension, I couldn’t wait to start using complex mathematical and physical models for concrete applications. Many aspects of our engineering work involve experimentation, preparing for a complex future regarding national security, law enforcement and military defence. In other cases, problem-solving is the key to realizing digital solutions for emerging real-world problems and threats.

Why should a talented physics graduate consider the Wireless Products team as a potential career pathway?

Ben at BAE Systems — “I love the whole creative process that’s needed to realize a technical and commercial outcome,” says early-career physicist Ben. (Courtesy: BAE Systems)

Working at the cutting edge is not something you can get just anywhere. Yet that’s exactly what we do day in, day out here at BAE Systems Digital Intelligence, delivering innovative next-generation technologies for our customers. I love the whole creative process that’s needed to realize a technical and commercial outcome. Put another way: you spend the bulk of your time coming up with new ideas, theories and clever solutions to address thorny science and engineering problems, applying all the physics domain knowledge you’ve learned along the way, and then you’re able to see your efforts take shape as an end-product in front of your eyes.

Another unique feature is the multidisciplinary nature of our programme. As such, there’s the opportunity to delve deep into one field – digital signal processing (DSP), for example, or radio-frequency propagation. Equally, we are encouraged to indulge our curiosity and become well-rounded scientists and engineers, at ease with the ambiguity that comes when working across a range of specialisms. That multidisciplinary mindset is a real differentiator and provides a solid basis for fast-track learning and development through your career.

What sort of R&D projects do you get to work on?

The high-level goal within the team is to use DSP to manipulate the electromagnetic world around us – and with a core emphasis on advanced software-defined radio (SDR) technologies. A case study in this regard is the Army Warfighting Experiment (AWE), where I was part of a cross-functional engineering team tasked with integrating three mission-critical applications into a multipurpose SDR platform.

The DSP was a stand-out feature of this R&D effort. We reworked intricate mathematics and implemented it onto a chip called a field-programmable gate array (FPGA) – essentially the crossover between hardware and software. Using this in conjunction with our DSP knowledge, we can manipulate the electromagnetic wave’s physical properties – such as its frequency, time characteristics and phase – to pull out information in innovative ways. On top of this are many layers of complex hardware, firmware and software such that when a user tells the radio to do something different to what it is currently doing, the radio will accomplish this task. It’s incredible how proud and excited the team felt when demonstrating the finished product for end-users.

What can early-career scientists expect in terms of training and development?

On reflection, one of the best aspects of the Wireless Products team is the fact that you are working in a department full of subject-matter experts across diverse fields of science and engineering. Even better, they are all willing to get stuck in to help anyone out. This on-demand support network is the best training you could wish for as an early-career physicist, creating the opportunity to broaden your knowledge base and become an established and reputable member of the team.

How about long-term career progression?

The Wireless Products team is a relatively young group of people – something that surprised me when I first got here. Even so, there’s a can-do culture with a lot of talented scientists and engineers who are more than ready – and willing – to take on leadership roles after just a couple of years in their roles. They want to be the best of the best and they’re encouraged in that regard by their colleagues and senior management.

That’s certainly my objective: to start leading development projects in the near- to medium term while working to become a “sphere of influence” – in other words, a domain expert in a technical niche where I can establish myself as the go-to expert within the company, even across the country. Overall, I can say that I am in the perfect place to constantly learn, to be challenged, to contribute as an individual as well as part of the collective – and framed within our ultimate objective of keeping people and society safe from harm. Bring on the next challenge!

Visit the Wireless Products team pages to find out more about specialist career opportunities at BAE Systems Digital Intelligence.

Applying physics to counter complex threats

The Wireless Products team within BAE Systems Digital Intelligence applies its cutting-edge capability in electronics and DSP to a range of complex challenges. These include:

Software radio and applications: developing and manufacturing high-performance software-defined radio hardware and software for applications in national security, law enforcement and military systems.
Surveillance technology: developing comprehensive end-to-end solutions for use in demanding operational security and environmental conditions.
Situational awareness: providing sensors and dedicated instrumentation to both capture and make sense of the acoustic or electromagnetic environment.
Advanced signal processing: interrogating complex, high-bandwidth data streams in real-time through the use of embedded DSP on FPGAs and software (e.g. C/C++/Java).
Specialist communications: delivering critical systems to enable military forces to communicate securely even in difficult electromagnetic environments – from submarines under the oceans through to geostationary satellites in space.

Novel machine learning approach reveals the hidden origins of cancers

Radiology and pathology assessments are the gold standard for diagnosing cancer. But for a small percentage of cancer cases these techniques fail to locate the primary site of a metastatic tumour, which is then classified as a cancer of unknown primary (CUP).

Such CUPs, which represent 3–5% of all cancers, pose unique challenges, such as difficulties in selecting an appropriate treatment plan. The lack of knowledge about the primary site hinders the prescription of precision drugs that are approved for specific cancer types. Such targeted treatments have been shown to be more effective and less invasive than broad-spectrum treatments. But patients with CUP often find themselves without such targeted therapies.

Now, a research collaboration from MIT and Dana-Farber Cancer Institute has come up with a potential solution to this long-standing problem. The researchers have harnessed the power of machine learning to develop a computational model that can predict the site of origin of CUPs.

Intae Moon and Alexander Gusev — **The team behind OncoNPC** Researchers Intae Moon (left) and Alexander Gusev (right). (Courtesy: Alexander Gusev)

In their study, published in Nature Medicine, Alexander Gusev and his team used machine learning to predict cancer type based on genetic data. By training their machine learning model on data from almost 30,000 patients diagnosed with 22 known cancer types, the researchers created a tool called OncoNPC. This tool successfully predicted the origins of about 80% of 7289 known tumour samples, and this accuracy rose to nearly 95% for tumours with high-confidence predictions (about 65% of the total). By analysing the genetic sequence of around 400 genes, OncoNPC can accurately predict the origin of tumours and, as such, could significantly improve treatment options for cancer patients.

Building on this success, the researchers applied the model to a dataset of 971 tumours from patients with CUP. The model accurately predicted the origin of at least 40% of these tumours, representing a significant improvement in treatment accuracy for this historically challenging group.

Moreover, the researchers correlated the model’s predictions with germline mutations, inherited genetic changes that can indicate a predisposition to certain cancers. The model’s predictions were notably aligned with the type of cancer suggested by the germline mutations, further validating its accuracy.

“That was the most important finding in our paper, that this model could be potentially used to aid treatment decisions, guiding doctors toward personalized treatments for patients with cancers of unknown primary origin,” explains lead author Intae Moon, an MIT graduate student.

The practical implications of this breakthrough are substantial. Survival data analysis demonstrated that CUP patients predicted by the model to have cancer with a poor prognosis indeed had shorter survival times, while those predicted to have cancer types with better prognoses showed longer survival times. Additionally, the model identified a group of patients who could have benefited from existing targeted treatments had their cancer type been known, potentially sparing them from broad-spectrum chemotherapy drugs.

Next, the researchers plan to enhance their model by integrating additional data, such as pathology and radiological images. This holistic approach could offer comprehensive insights into tumours, facilitating predictions not only about the cancer type and patient outcomes, but even potentially guiding optimal treatment decisions.

With the convergence of machine learning and medical science, this advanced research shines a light on the future of personalized cancer treatment for patients whose cancers have long puzzled the medical community.

Physics of salt water taffy, young Einstein on the BBC, auction opens for Newton’s trees

Salt water taffy is a sweet treat that can be found at many US beach resorts. It is made by boiling table sugar, water, oil, corn syrup, colours and flavourings. The mixture is then cooled and stretched – either by hand or machine. This aerates the candy and breaks down larger oil droplets. The material is then rolled and cut into small pieces that are wrapped and sold.

Coming in a wide variety of colours, salt water taffy (which doesn’t actually contain any salt water) is a viscoelastic material – which means that it’s somewhere between a viscous liquid and an elastic solid. Researchers have now discovered why salt-water taffy is viscoelastic, finding that the air bubbles and the oil droplets determine the taffy’s mechanical properties.

“Oil droplets and air bubbles are like rubber balls and when deformed in the taffy, they tend to return to their original, spherical shape because of surface tension,” says Okinawa Institute of Science and Technology researcher San To Chan. “Emulsification and aeration make taffy more elastic, hence, chewier.” The more important question, however, is how do you stop the taffy from sticking to the roof of your mouth, or wreaking havoc with dental work.

Miraculous year

In 1905, the 26 year old Albert Einstein published five ground-breaking papers that helped usher in the era of modern physics. As well as developing the special theory of relativity that year, Einstein also delivered profound insights into Brownian motion and the photoelectric effect – the latter providing early evidence for quantum theory.

This annus mirabilis is explored by the BBC’s resident polymath Melvin Bragg in his excellent radio programme In Our Time. Bragg is joined by three science historians and Einstein experts – Richard Staley, Diana Kormos Buchwald and John Heilbron – who provide fascinating insights into the 20th century’s most famous scientist. You can listen to the programme here.

Newton's tree — Gravitational pull: this apple tree at Woolsthorpe Manor is believed to be the one that inspired Isaac Newton. (Courtesy: Bs0u10e01/CC BY-SA 4.0)

Back in April, when the ancient apple tree said to have inspired Isaac Newton’s theory of gravity was coming into blossom, the UK’s National Trust announced that it would be auctioning ten saplings from the tree. That auction has now opened, and you have until 20:00 BST on 29 September 2023 to get in your bid.

The trees have been grown by Blue Diamond nurseries and up to 50% of proceeds raised from the auction will go to the National Trust and Woolsthorpe Manor. The latter being Newton’s birthplace and family home in Lincolnshire. The reserve price for each tree is £500 and you can make your bid here, or see the current highest bids.

How I realized I could not count

I once spent a month in Kenya taking part in a study to see if it is practical to disinfect water with sunlight. For various reasons, I ended up spending my first week confined to base, in the hills outside Nairobi, twiddling my thumbs as I waited for an off-road vehicle to take me to my destination. Mike, who was head of the charity I was working for, could see I was bored to tears and so, on my fifth day in the country, asked me if I would like to help at their mobile clinic in the Maasai bush as their usual pharmacist was unavailable.

Me: You do know I’m not medically qualified.

Mike: Yes. We have our own doctor and our own nurses. I want you to act as substitute pharmacist.

Me: I’m just as unqualified to be a pharmacist as a clinician.

Mike: Don’t worry. You’ll be in charge of the pharmacy trunk. The patients will be seen by the medical team. If medication is required, they’ll write the type and number of pills on the outside of an envelope and give the envelope to you to fill. Serune – our interpreter – will be with you and he will tell the patient how many and how frequently they should take the pills. Your only job will be to count the pills into the envelope.

I therefore found myself driving through the southern Kenyan bush to a rural school, where we were going to set up our mobile clinic. In fact, when we arrived there was already a long queue of Maasai people waiting for us. Desks were taken out and placed in the shade of a tree. I was given the pharmacy trunk and the local doctor told me which pills would be used for which conditions.

Not being able to speak the local language, I was glad to have Serune next to me to translate. The medical team playfully announced to the waiting crowd they had a distinguished university professor from a medical college in Ireland assisting on the pharmacy desk. What could possibly go wrong?

I saw Serune looking at the jumble on the plate. How on earth could he know how many pills there were?

My first customer arrived soon afterwards with instructions emblazoned on an envelope: “Pills for malaria, one to be taken four times per day for seven days (28 pills)”. I poured about 28 pills onto a plate and start counting.

Me: One, two, thr…

Serune: 26. You have 26 tablets there.

I saw Serune looking at the jumble on the plate. How on earth could he know how many pills there were? I know how important it is to be accurate in such matters. So I decided to confirm Serune’s thinking for myself.

Me: Four, five, si…

Serune: 26. I’m telling you Dr Kevin, you have 26 pills there.

Undeterred, I carried on counting the pills. All 26 of them. So I added another two and gave the filled envelope to Serune who explained to the elderly lady how and when they should be taken.

A woman carrying a baby outside a hut in rural Kenya — **Slow learner** While in Kenya, Kevin McGuigan found that he couldn’t count anywhere near as fast as people in Maasai, including his interpreter Serune, whose home is pictured here. (Courtesy: Kevin McGuigan)

Next to arrive was one of the Maasai elders, who brandished an envelope requesting “Antibiotic pills, one to be taken twice per day for seven days (14 pills)”. I opened the containers of antibiotics, poured out what I thought was approximately 14 pills onto a plate and started counting.

Me: One, two, thr…

Serune: 16, you have 16 pills there.

Me: Three, fou…

Serune: Dr Kevin how can you not see that you have 16 pills there?

At this point the elder said something in the local dialect that made Serune burst out laughing. After I counted to 16, removed the two surplus pills and sent customer number two happily on his way, I asked Serune what he found so funny. Apparently, the elder had quipped that he has a four-year old granddaughter who can count faster than the professor from the medical college.

We refined our procedure so that for the rest of the day, I did all the pouring and Serune did all the counting. Our work rate quadrupled. That evening, as we drove back home, I asked Serune how the local people could count so fast and so accurately. What was the secret to their amazing numeracy?

He explained that from the age of seven, each Maasai child is given a number of goats to look after. The goats forage in the bush and the goatherds need to know where they are and if any are missing. When the child reaches the age of 14, they do the same with the more valuable cattle. As a result, Maasai children develop quick and efficient counting skills. For them, it’s almost a type of pattern recognition and they were incredulous that a fully grown adult should find it so hard to count.

Although I didn’t realize it then, I now know that the way that the Maasai count has several names: subitizing; number sense; number discrimination. All refer to the ability to know immediately how many items lie within a visual scene. In fact, researchers in Italy have recently shown that the pupils of our eyes dilate involuntarily when we count large numbers of things, to assist in this process.

In total, I worked with the Maasai community for nearly 10 years. In that time, they taught me many things, including the true meaning of respect, kindness and generosity of spirit. However, to my great regret, they never quite managed to teach me the knack of how to count like they can.

Walk-through PET scanner made for high-throughput imaging at lower cost

The use of positron emission tomography (PET) for disease diagnosis and repeated monitoring of the effectiveness of medical treatments is on the rise, with the number of required scans increasing at an estimated rate of about 11% per year. Keeping up with this demand may pose challenges to radiology departments, generating a need for PET scanners that are faster to operate, less costly to purchase and require fewer scan-related personnel resources.

With this aim, researchers at Ghent University in Belgium are developing a novel patient-centred upright imaging device for total body PET – the walk-through TB-PET. Their proposed TB-PET design, which is visually similar to an airport security scanner, is expected to be over three times cheaper than a cylindrical long axial field-of-view (LAFOV) system and reduce radiographer/technologist time by more than half of that required for standard axial field-of-view (SAFOV) PET scanners.

The walk-through device will employ monolithic detectors with depth-of-interaction (DOI) capabilities and high intrinsic spatial resolution to produce high-quality PET images in sub-minute scans.

Writing in the European Journal of Nuclear Medicine and Molecular Imaging, the researchers describe the dual flat-panel design of the walk-through TB-PET and present performance comparisons – in terms of component costs, system sensitivity, patient throughput and required dose per patient – with a SAFOV PET scanner (Biograph Vision 600) and a LAFOV scanner (Vision Quadra). They note that the comparison presumes the walk-through scanner will be used for efficient routine clinical PET imaging, and is therefore based on scans of only the torso and head.

Principal investigator Stefaan Vandenberghe and co-researchers have proposed a new design concept for PET imaging that relies on two opposing flat-panel detectors that can be brought as close as reasonably possible to the patient (standing upright between them) to increase both sensitivity and spatial resolution.

The team selected monolithic detectors that offer two to three times higher spatial resolution than the pixelated detectors used in today’s clinical PET systems. The ability of monolithic detectors to encode DOI information provides a uniform spatial resolution of just below 2 mm over the whole field-of-view. These detectors have an expected coincidence timing resolution between 200 and 400 ps.

Design of a walk-through total-body PET system — **Walk-through TB-PET** (a) Artist view, (b) flat-panel design, (c) handlebars reduce body motion, (d) the mock-up used for patient throughput measurements; (e) the modules on each panel side can be manually adjusted. (Courtesy: CC BY 4.0/*Eur J Nucl Med Mol Imaging* 10.1007/s00259-023-06341-x)

The walk-through TB-PET scanner is composed of two flat panels, each about 70 cm wide and 106 cm high, with a 50 cm gap between them. Each panel consists of a 14 × 20 array of monolithic bismuth germanate (BGO) detector blocks, 50 × 50 × 16 mm in size, read out by an array of 6 x 6 mm silicon photomultipliers. The team derived the scanner size and flat panel dimensions using body measurements obtained from PET/CT images of 40 randomly selected patients from CHU de Liège.

During a scan, the patient will stand between the two flat-panel detectors. Crucially, this walk-through design removes the need for time-consuming positioning of the patient on and off the bed. Another advantage is the system’s small footprint, which only requires about 2–6 m² of dedicated space, a fraction of the installation spaces required for today’s PET imaging suites (35–40 m²). Scanner cooling requirements should also be less.

The workflow comparison generated impressive findings. Vandenberghe and colleagues estimated that the walk-through TB-PET could scan up to 87 patients during an eight-hour shift, in comparison with 53–60 patients for the LAFOV scanner and 28 for the SAFOV system.

The researchers estimated the cost of their proposed scanner based on monolithic BGO or lutetium-yttrium oxyorthosilicate (LYSO) scintillators, as well as the cost of the silicon photomultipliers, which represent the two main expenses in a PET scanner. They determined that the component cost for a BGO-based walk-through TB-PET is 3.3 times lower than that of a LAFOV system with a 106 cm axial field-of-view, and just 20% higher than that of a SAFOV scanner.

After constructing a mock-up of the scanner, the researchers discovered that the addition of handlebars could significantly reduce the motion of a patient in a standing position. They are also using the mock-up to determine whether breath-hold is feasible with 30 s acquisitions, and plan to test techniques for motion estimation and correction.

Other future plans include constructing a system by assembling the detectors into modules, building a patient platform with automated patient height adjustment of the flat panels, and integrating motion detection. Ultimately, the researchers aim to integrate the walk-through scanner with a standing CT to combine molecular imaging with high-resolution anatomical imaging. They also hope to further reduce the PET and CT dose using advanced deep-learning-based noise reduction methods.

Browse articles by content type