Biogenic optical devices: The glass-like shells of diatoms help turn light into energy in dim conditions. (Courtesy: McGill University)
The silica shells of single-celled marine algae known as diatoms may have evolved to capture wavelengths of light found in the Sun’s spectrum. This finding, from researchers at McGill University in Canada, could have applications for solar energy because the shells, or frustules, are made from glass and are similar to materials already used in photonic chips and solar panels.
Diatoms evolved over millions of years to survive in any aquatic environment, including regions of the ocean that receive very little light. They owe this adaptability to the excellent optical response of their frustules, which are tens of nanometres thick and covered in pores separated by surprisingly regular distances. These pores respond to light differently depending on their size, spacing and configuration.
In the new work, a team led by David Plant and Mark Andrews sought to understand how the frustules function as a biophotonic device. To do this, they imaged different sections of the structures using four high-resolution microscopy techniques: scanning near-field optical microscopy; atomic force microscopy; scanning electron microscopy; and dark field microscopy. They then used these images to build a series of models to analyse each part of the frustule via three-dimensional simulations. These models showed how different wavelengths of light interact with the structures – including when it is captured and distributed; how long it is retained; and how it is likely absorbed by the cell, explains team member Yannick D’Mello.
Photosynthesis even in dim conditions
The results revealed that the wavelengths of light the frustules interacted with coincided with those absorbed during photosynthesis, suggesting that the structure could have evolved to capture sunlight in an optimum way. The results also showed that the frustules redistribute light so that it is absorbed across the plant cell. In addition, the team found that light circulates inside the frustule long enough for photosynthesis to occur even in dim conditions deeper underwater.
The new work could make it possible to cultivate diatom species that harvest light at different wavelengths for technological applications. The light absorption mechanisms the researchers discovered could also be used to improve the way solar panels absorb light – for example by allowing light to be collected at more angles, thereby avoiding the need for the panel to be directly oriented towards the Sun.
The study, which is detailed in Optical Materials Express, is part of D’Mello’s PhD thesis, which focuses on solar energy harvesting on a silicon photonic chip. He and his colleagues are now working on upgrading their model and applying it to other diatom species. “We will also investigate how frustules can be combined with silicon photonics and solar energy harvesting technologies to improve its efficiency, cost and scalability,” D’Mello tells Physics World.
Ordinarily, light transmits the same in both directions: if I can see you, you can see me. Now, however, researchers have created a device that uses travelling sound waves to break this symmetry, thereby reducing unwanted optical phenomena such as backscattering. The new device is the first to produce this beneficial effect for selective optical vortices, which are used in optical communications, and it could also have applications for optical tweezers and vortex-based lasers.
Vortices are ubiquitous in nature – in gases, fluids, plasma and DNA, for example. In optical vortices, the wavefront of a beam of light spirals around the beam’s central propagation axis, taking on a helical shape with zero intensity at the core. This spiralling effect comes about because light carries orbital angular momentum (OAM). This form of angular momentum is distinct from the more familiar spin angular momentum, which manifests itself in polarization, and was only discovered in 1992.
Because information can be encoded in OAM, optical vortices show much promise for multiplexing, which is the process of sending multiple optical signals down a single fibre with minimal interference or other detrimental effects. As yet, however, it has been challenging to make devices in which certain vortex models propagate in one direction only. This is due to a fundamental principle of optics known as reciprocity, which implies that light signals will propagate freely in both directions through an optical fibre. Such two-way traffic can cause problems like backscattering that reduce the strength of the transmitted signal.
Sound waves manipulate optical waves
A team led by Xinglin Zeng, Philip Russel and Birgit Stiller of the Max Planck Institute for the Science of Light has now used propagating sound waves to break this light transmission reciprocity for chosen vortex models. In their work, they used the sound waves to manipulate optical waves in a chiral photonic crystal fibre via an interaction known as topology-selective stimulated Brillouin-Mandelstam scattering. The researchers explain that as the sound waves travel in one direction, they naturally enable non-reciprocal behaviour for the optoacoustic interaction. In this way, OAM modes can be either strongly suppressed or amplified, preventing random backscattering and thus minimizing signal degradation.
Stiller and colleagues report that their new device can be reconfigured as an amplifier or as an optical vortex insulator by adjusting the frequency of the control signal. Indeed, they demonstrated a vortex isolation of 22 decibels, which compares well with the best fundamental mode isolators that use stimulated Brillouin-Mandelstam scattering.
According to Stiller, potential applications of the device include OAM-based quantum communication and entanglement schemes as well as classical optical communications that use OAM modes (both fundamental and higher order) to increase the capacity of the communication channels. “The possibility of selective manipulation of vortex modes by light and sound waves [is] a very fascinating concept,” Stiller says.
The researchers, who detail their work in Science Advances, now plan to study more exotic sound waves that have unusual structures. “We want to see how they these waves interact with light in chiral optical fibres,” Stiller tells Physics World.
This January, something at Physics World changed. It took place right before our eyes, but practically no-one noticed. It concerns the body text of all articles in the print version of Physics World magazine, which had been set in a font called Dutch 801 for more than 15 years. Now, however, they are in Minion Pro. Headlines, standfirsts and captions, meanwhile, use a subtly different version of Franklin Gothic.
How could such a radical and transparent makeover have been missed by our print readers? To find out, I sought out Robert Bringhurst, whom I consider the leading authority on typography. Based on an island north of Vancouver in British Columbia, Bringhurst is the author of The Elements of Typographic Style, which was first published in 1992 and has been revised over half a dozen times since. The 400-page book is a compendium of everything there is to know on typography – its forms, histories and explanations – written with sparkling prose and astute observations.
The realm of typography is a “magic forest”, according to Bringhurst, endowing human language with “a durable, visible form, and thus with an independent existence”. While some areas in that forest are well travelled, many are spectacular and wild. In the far-out font Beowolf, for instance, computers introduce tiny random perturbations into the letters, making each slightly dissimilar and reading them a surprisingly fresh experience.
Physicists might not realize, but typography has a huge impact on the reading experience. Bad design, Bringhurst says, makes “the letters mill and stand like starving horses in a field”, while careless design makes them “sit like stale bread and mutton on the page”. Good design involves an “energetic repose” whose paradoxical ambition is to draw our eyes in and then vanish. The late Beatrice Ward, Bringhurst’s scholarly predecessor, compared typography to a crystal goblet, “because everything about it is calculated to reveal rather than hide the beautiful thing which it was meant to contain”.
Moreover, Bringhurst writes, choosing a font is like framing a painting in that it has to suit the contents. Think, he says, of how silly “a Cubist painting in an 18th-century gilded frame” would be. Or, closer to home, imagine if you had to read page after page of Physics World in Comic Sans – the supposedly playful font adopted in many cheesy PowerPoint presentations and even by future CERN boss Fabiola Gianotti when she announced the discovery of the Higgs boson in 2012.
Food and wine
I asked Bringhurst how readers typically react to new fonts. “It’s the same range of reactions you could expect if you changed the tableware and cutlery in a restaurant,” he replied in an e-mail. “In the journal and the restaurant both, it is presumably the food that really counts, but presentation counts for something too, and so it should. Reading, like eating, is partly, but only partly, a physical act.”
The presentation, Bringhurst continued, reveals the conscientiousness of the presenter. “I think that publishers, like civil engineers, highway maintenance workers and the gardeners tending the flowers in public parks, are morally obliged to do a good job because part of the social fabric – and a pretty important part of the social fabric – is in their hands.”
I pointed out that not everybody had a free hand in choosing a presentation. Those running magazines, for example, have to rely on expensive computer languages and formats developed and licensed by multinational corporations. “Of course, they stand outside the magic forest,” Bringhurst responded. “Publishing businesses have to be economically sound, so they can’t and don’t make purely ethical or aesthetic decisions.”
Font of all knowledge In January 2023 the body text of articles in Physics World print magazine switched from Dutch 801 to Minion Pro font – but can you imagine if, say, Broadway were used? (Courtesy: IOP Publishing)
Physics World couldn’t. When the magazine’s production switched from scissors and paper to desktop publishing in the early 1990s, it used a technology recently developed by the computer software company Adobe. In that technology, a computer language called PostScript had been used to create a package of “Type 1” formats to display a variety of fonts – Dutch 801 and Franklin Gothic among them.
Dutch 801, however, lacked a full Greek alphabet and many mathematical symbols, so Physics World had to supplement it with Symbol, another Type 1 font. It was a messy compromise. Even when Adobe co-developed another format, called OpenType, in the late 1990s, Physics World and other publications held on. They’d invested so heavily in the Type 1 fonts that there was no huge reason to change.
Then, in 2021, Adobe announced that it would stop supporting Type 1 fonts by the end of 2022, forcing Physics World to finally switch. The advantage of Minion – one of Adobe’s new OpenType offerings – is that it is very similar to Dutch 801 and fits about the same amount of text on the page. Physics World’s OpenType version of Franklin Gothic, meanwhile, was found from somewhere else. When I explained the shift to Bringhurst, he called it “a conservative but very good decision”.
The critical point
Typography is a curious case of something that involves both what philosophers call an “embodiment” relation, in which you perceive the world through something (like your glasses), and a “hermeneutic” relation, in which you look at a technology to read the world (like the numbers on a thermometer). Typefaces aspire to be both simultaneously, though they can be distracting if they call too much attention to themselves; imagine reading all of Physics World in the Broadway font (see illustration above).
Let me confess, I would not have noticed the typographic change had it not been for an editor’s passing remark. And if you’re reading this article on the Physics World website or the digital version of Physics World, the typography is unchanged, for the fonts were already suited for the digital experience. Like everyone else, I’m more interested in the food on the table and the wine in the goblet. But at least I’m now a little more appreciative of what it takes to put it there.
Cerebral venous sinus thrombosis (CVST) is a clot in the veins that drain blood away from the brain, and is one of the most common causes of stroke in young people. Early diagnosis and anticoagulant therapy can minimize the damage and mortality associated with CVST, but current treatments fail in some 20–40% of cases.
To improve clinical outcomes, a research team headed up at North Carolina State University and Georgia Institute of Technology has developed a novel vortex ultrasound tool designed to break down blood clots in the brain. The device, which the team describe in Research, eliminated clots faster than existing techniques, and could restore blood flow through a completely blocked in vitro model of CVST in just 8 min.
In a technique known as sonothrombolysis, ultrasound is used to cavitate microbubbles surrounding a clot, causing it to break down. Compared with conventional anticoagulant or thrombolytic drugs that dissolve the blood clot, sonothrombolysis has potential to remarkably reduce the required treatment time. Previous strategies, however, have not been clinically effective when treating large, completely occluded veins or arteries.
What’s different about this new approach is that instead of using conventional planar ultrasound, the team has developed a novel vortex transducer that creates a helical wavefront, in which the ultrasound swirls tornado-style as it moves forward. This vortex ultrasound induces a shear stress parallel to the clot’s front surface, which mechanically disrupts the clot fibrin networks layer by layer to dissolve the clot more efficiently. The shear stress also loosens the clot structure, improving the delivery of microbubbles and any thrombolytic agents.
“Our previous work looked at various techniques that use ultrasound to eliminate blood clots using what are essentially forward-facing waves,” explains co-corresponding author Xiaoning Jiang from NC State University in a press statement. “Our new work uses vortex ultrasound, where the ultrasound waves have a helical wavefront. Based on our in vitro testing, this approach eliminates blood clots more quickly than existing techniques, largely because of the shear stress induced by the vortex wave.”
Generating a helical wave
The researchers created a vortex ultrasound transducer using a 2 x 2 array of small-aperture, low-frequency (1.8 MHz) piezoelectric transducers. Assembling the array with a quarter-wavelength (0.21 mm) shift between the forward-viewing surfaces of neighbouring transducers induces the physical phase delay required to generate a helical wavefront.
High-speed sonothrombolysis Left: prototype of the vortex transducer and a nonvortex transducer installed in a catheter. Right: the measured acoustic pressure map for a vortex and a nonvortex transducer. (Courtesy: CC BY/Research 10.34133/research.0048)
The transducer array is small enough to fit into a 3.0 mm-diameter catheter, with a lumen to deliver the microbubble cavitation agents and drugs. This catheter can then be fed through the circulatory system to the site of the blood clot.
In tests on a blood vessel phantom, the vortex transducer recanalized the entire length of a 50 mm clot (restoring blood flow) within a 30 min treatment, while a nonvortex transducer achieved less than 50% of clot lysis (breakdown) and did not recanalize the vessel. Comparing clot lysis speed, the vortex transducer had an absolute lysis rate of 53.9 mg/min, 64.3% higher than that of nonvortex transducer-based thrombolysis (32.8 mg/min).
“Based on available data, pharmaceutical interventions to dissolve CVST blood clots take at least 15 hours, and average around 29 hours,” notes co-corresponding author Chengzhi Shi from Georgia Tech. “During in vitro testing, we were able to dissolve an acute blood clot in well under half an hour.”
Safe and effective
Jiang, Shi and collaborators tested their vortex transducer in a 3D-printed model of the cerebral venous sinus. They found that a completely blocked blood vessel was fully recanalized in only 8 min of treatment. The acute clot mass was 3.1±0.3 g before treatment and 1.2±0.4 g after, corresponding to a reduction rate of 7.66 %/min and a lysis speed of 237.5 mg/min. The team note that these values are significantly higher than those recently reported for drug-free endovascular sonothrombolysis (1.3–2.5 %/min; 2–4.6 mg/min).
Analysis of the clot debris revealed that most particles were less than 100 µm in size, reducing the risk of dangerous embolus formation. To further assess the treatment safety, the researchers applied vortex ultrasound to ex vivo canine jugular veins, observing no damage to the blood vessel walls. They also determined that vortex ultrasound does not cause substantial damage to red blood cells.
Next, the researchers plan to perform tests in an animal model. If these are successful, they hope to pursue clinical trials. “In severe cases of CVST and in patients with massive, fully blocked venous clots and who cannot be effectively treated with medications that are currently available, the vortex ultrasound thrombolysis technology may become a life-saving treatment in the future,” they conclude.
In the classic 1991 film Terminator 2 Arnold Schwarzenegger’s robot assassin, the T-800, comes up against a next-generation model: the T-1000 Advanced Prototype. It is made from a liquid metal called “mimetic polyalloy”, which allows it to reform into any shape.
The T-1000 is able to slip through narrow openings by oozing into its fully liquid form, as well as reforming itself without suffering physical damage.
They did this by embedding magnetic particles in gallium, a soft metal with a low melting point. Applying an alternating magnetic field not only heats the magnetic particles, making the body become a liquid, but also allows it to become mobile.
In one video released by the team, a 10 mm-tall LEGO-like minifigure liquifies to ooze before passing through bars in a mock-up prison cell. It then cools inside a mould and the figure forms back into its original shape.
The authors think that the technique could have medical uses such as removing foreign objects from inside the body or to deliver drugs in hard-to-reach places. Let’s hope it doesn’t stretch to morphing killer robots.
The intricate, twisting shapes are based on the Chua circuit — an electronic system that was invented in 1983 and is thought to be one of the first proofs of chaos. An ordinary circuit produces an oscillating current, but Chua’s circuit results in oscillations that never repeat. Computer simulations of the circuit display chaotic shapes called “strange attractors”.
The team got in touch with goldsmiths to recreate the attractor patterns but it proved too tricky using traditional techniques. They then turned to 3D printing to create a mould that was then used by the goldsmiths to successfully create the designs.
The team now plan an exhibition based on chaos that can be adapted for international museums and say that the jewellery could be used for educational purposes.
“Jewellery seemed the best way to interpret the beauty of chaotic shapes,” notes Eleonora Bilotta. “Touching and wearing them was also extremely exciting”.
Heat sink
And finally, 22 January marked Chinese New Year where the year of the tiger made way for the year of the rabbit.
During the week-long celebration, work is suspended, businesses close and nearly three billion people leave the city to join their families in rural areas. According to a new study, the holiday is not only the largest short-term suspension of human activity on Earth but is also associated with lower temperatures in major Chinese cities too.
The study found that the urban heat island intensity – the difference in temperature between urban areas and their rural surroundings — dropped by 33% on average in 31 Chinese cities. This corresponded to an average drop in surface air temperature of 0.35 degrees Celsius. Chilly.
The LIGO–Virgo–KAGRA collaboration has announced that the search for gravitational waves will resume in May. The next observational run – the project’s fourth – was meant to start last year but was postponed due to a series of engineering delays resulting from the COVID-19 pandemic. The run will be the longest to date, operating for 18 months.
Gravitational-wave detectors are L-shaped interferometers with arms several kilometres long. Laser beams are sent down each arm and then bounce off mirrors, called test masses. The beams are then recombined at the centre of the interferometer producing an interference pattern that cancels out when perfectly aligned. The instruments are thus sensitive to minute changes in length caused by any passing gravitational waves.
LIGO has been a huge success, spotting its first gravitational wave in 2016 from a binary black-hole merger. Since then another 92 detections have been made over three observational runs. Observational run 3 was supposed to last 12 months until the end of April 2020 but ended on 27 March 2020 when the pandemic started.
The LIGO and Virgo detectors then underwent a series of sensitivity improvements, which included ways to suppress “quantum noise” in the detector. “[This] limits the sensitivity of the gravitational-wave detectors both at low frequency, in the form of radiation pressure noise, and at high frequency, in the form of photon counting noise,” says Alessandro Bertolini from the Nikhef institute in Amsterdam, who works on detector development.
The upgrades are expected to double the sensitivity of the detectors to neutron star mergers. Whereas gravitational waves were detected almost every week in the previous observational run, such events should now be picked up every day.
Three’s a crowd
As well as featuring Virgo and LIGO, Japan’s KAGRA detector will also join the upcoming run. KAGRA, which is located under a mountain in central Japan, became operational in 2019 and joined the previous run in February 2020 before it was cut short due to the pandemic.
While KAGRA is currently poorer than Virgo and LIGO at detecting gravitational waves, its sensitivity will also soon improve thanks to detector upgrades. KAGRA will operate for one month in the upcoming run before being shutdown for improvements. It is hoped that KAGRA will re-join observations for at least three months next year.
“We hope to realize our first detection by the end of the coming run,” KAGRA spokesperson Jun’ichi Yokoyama from the University of Tokyo told Physics World. “How much our participation will contribute to the science obtained by the entire network depends crucially on the sensitivity we will achieve by the end of the run, which is difficult to answer at this point.”
After the fourth run, the LIGO and Virgo detectors are expected to undergo further upgrades, particularly to the coatings used on the mirrors. “The new coatings are currently still in a development phase,” says Bertolini. “[The upcoming] run will allow the scientific output to be increased while the coating design is finalized, and the new test masses are prepared for the following run.” The new coating is expected to be ready for the fifth observational run, which begins in 2026.
Heat transfer under pressure: A boron arsenide crystal placed between two diamonds in a controlled chamber with thermal energy transported under extreme pressure. (Courtesy: Y Hu)
The thermal conductivity of materials usually increases when they are subject to very high pressures. But researchers at the University of California, Los Angeles (UCLA) have found that the opposite is true for boron arsenide – a newly discovered semiconductor that shows much promise for heat management applications and advanced electronics devices. The finding could change the way we think about heat transport under extreme conditions, such as those found in the Earth’s interior, where direct measurements are impossible.
The researchers, led by Yongjie Hu, applied hydrostatic pressure to boron arsenide samples placed between two diamonds in an anvil cell. They then examined how the atomic vibrations of the crystal lattice (phonons, the main way by which heat is carried through materials) changed with increasing pressures of up to 32 GPa. To do this, they employed a variety of ultrafast optics measurements, including Raman spectroscopy and inelastic X-ray scattering. The team found that at extremely high pressure – hundreds of times higher than that found at the bottom of the ocean – boron arsenide’s thermal conductivity begins to decrease.
Hu and colleagues, who report their work in Nature, attribute the anomalous high-pressure behaviour they observed to a possible interference caused by the competing ways in which heat travels through the boron arsenide crystal as the pressure mounts. In this case, the competition is between three-phonon and four-phonon scattering processes. In most common materials the opposite effect is observed: as pressure squeezes atoms closer together, heat moves through the structure faster, atom by atom.
A mechanism for an internal thermal window
The results also suggest that the thermal conductivity of materials can reach a maximum after a threshold pressure range. “We are very excited to see this finding breaking the general rule of heat transfer under extreme conditions and it points to new fundamental possibilities,” Hu tells Physics World, “The study could also impact our established understanding of dynamic behaviours such as for the interiors of planets. There may even be implications for outer space explorations and climate change.”
Hu’s colleague, co-author Abby Kavner adds, “If applicable to planetary interiors, our findings may suggest a mechanism for an internal ‘thermal window’ – an internal layer within the planet where the mechanisms of heat flow are different from those below and above it.”
There might be other materials experiencing the same phenomenon under extreme conditions that break the classical rules, Hu says. Indeed, the new findings might help in the development of novel materials for smart energy systems with built-in “pressure windows” so that the system only switches on within a certain pressure range before shutting off automatically after reaching a maximum pressure point.
This episode of the Physics World Weekly podcast features an interview with Danna Freedman, who uses synthetic chemistry to create quantum bits (qubits). Based at the Massachusetts Institute of Technology, Freedman explains how this bottom-up approach allows her team to create quantum technologies on a molecular scale.
Freedman explains why this approach could be used to create high-performance quantum sensors with a wide range of applications. These include biocompatible sensors that could someday be incorporated into medical devices. She also talks about another aspect of her research that focuses on materials under extremely high pressures – and chats about the connections between the quantum and high-pressure worlds.
High-resolution imaging (A) Example FLASH images of the cerebellum and cerebrum; boxes indicate zoomed portions. (B) T2*-weighted magnitude images; the cortical depth was sampled from white matter (red) to the cerebrospinal fluid (yellow). (C) Phase image showing contrast in the cerebellar cortex (arrows). (D) T1 map. (Courtesy: CC BY 4.0/Radiology 10.1148/radiol.220989)
The cerebellum, a small region of the brain located at the back of the head, is largely responsible for motor control, as well as being involved in behaviour and cognition. It also plays a role in various disease processes, such as multiple sclerosis (MS), for example, which causes extensive demyelination in the cerebellar cortex. But despite its importance, the structure of the cerebellum has not been fully investigated due to the inadequate resolution of current in vivo imaging techniques.
The key obstacle is that the cortex covering the cerebellum comprises extremely tightly folded layers of tissue and requires high-resolution imaging to fully visualize and study its anatomy. Now, researchers at the Spinoza Centre for Neuroimaging in the Netherlands have developed a method to image the cerebellar cortical layers using a powerful 7 T MRI scanner, describing the technique in Radiology.
First author Nikos Priovoulos and colleagues modified two MRI pulse sequences that image the cortical surface and intracortical layers, to translate the high signal-to-noise ratio of 7 T MRI into high spatial resolution. By also compensating for motion, they generated images of up to 200 μm resolution, with a clinically applicable scan time of less than 20 min.
For their study, the researchers imaged healthy participants in a 7.0 T MRI scanner. To image the layers within the cerebellar cortex, they used a T2*-weighted fast low-angle shot (FLASH) sequence with a 210 × 210 × 15 mm field-of-view (FOV) and a voxel size of 0.19 × 0.19 × 0.5 mm. They used this scan, which covers only part of the cerebellar cortex, to image nine subjects.
With such a small voxel size, involuntary motion can limit the effective spatial resolution. To combat this, the researchers interleaved the FLASH sequence with whole-head fat images, which they used to estimate and correct for motion. In four participants who underwent scans both with and without this step, prospective motion correction improved image sharpness and preserved high-resolution features.
The motion-corrected FLASH scans visualized inner- and outer-layer structures in the cerebellar cortex for all participants. The researchers suggest that these represent the deep, iron-rich granular layer and the less neuronally dense superficial molecular layer, which exhibit differences in magnetic susceptibility at 7.0 T. They note that cerebellar layers are differentially affected in diseases such as MS, thus the ability to observe individual layers could provide valuable diagnostic markers.
“In MS the cerebellum plays an important role,” explains Priovoulos in a press statement. “MS patients have motor lesions, which means that they have damage to the nerve cells involved in movement. Based on previous findings, we know for MS specifically that we could benefit from high-resolution imaging in the cerebellum.”
Unfolding the cerebellum
The researchers also used 7 T MRI to visualize the entire cerebellum in nine healthy participants. Here, they employed a magnetization-prepared 2 rapid gradient-echo (MP2RAGE) sequence with a 210 × 120 × 60 mm FOV and a voxel size of 0.4 mm3. They used the same fat navigator for motion correction.
The motion-corrected MP2RAGE scans resolved cerebellar anatomic features down to individual folia – the tiny folds in the cortical surface. The team, led by Wietske van der Zwaag, note that downsampling the data to match current state-of-the-art MRI acquisitions reduced the visibility of these features.
MP2RAGE scans (A) Whole-cerebellar cortex image; boxes indicate zoomed portions. (B) White matter segmentations. (C) Pial surface segmentations. (D, E) High-fidelity segmentations allow visualization of the cerebellar cortical surface. (Courtesy: CC BY 4.0/Radiology 10.1148/radiol.220989)
The high spatial resolution of the images allowed the researchers to computationally unfold the cerebellar cortical surface into a continuous sheet. This enabled them to calculate clinical measures such as the cortical surface area and thickness, and examine disease-related factors such as myelin-sensitive T1 values.
The estimated median cerebellar cortical surface area was 949 cm2 (176%–759% larger than previous imaging-based in vivo estimates) and the median cerebellar cortical thickness was 0.88 mm, in agreement with ex vivo reports and four to five times thinner than current imaging-based in vivo estimates.
While most participants in the study were young (a median age of 36), the team included two older subjects (aged 57 and 62). MR images of these participants showed visible cortical thinning in the cerebellum at visual inspection and lower cerebellar cortical thickness and grey matter T1 values than in the younger cohort.
“This is the first time that we can view the human cerebellum directly in living humans, with this much detail,” says Priovoulos. “We can do this specifically because we have a very high-field magnet (which is expensive and hard to build) and also motion correction, because people tend to move during the scans.”
Priovoulos, van der Zwaag and PhD student Emma Brouwer are now working to make the MRI signal in the cerebellum more reliable. “The wavelength of the MRI signal at 7 T is comparable to the human head size and this frequently makes the signal in the cerebellum inhomogeneous,” Priovoulos tells Physics World. “To tackle this, we are trying to combine our setup with multiple radiofrequency producing coils to optimize signal generation. The challenge is to do so while still keeping the scan length short and the setup translatable to the clinic.”
The researchers are already applying the 7 T MRI approach to scan patients with MS. They also want to use it to better understand cerebellar ataxia, a muscle-control disease. Alongside, they are using functional 7 T imaging, along with the cerebellar anatomical reconstruction, to examine cerebellar functional responses in detail and explore the role of the cerebellum in human health and disease.
As the climate crisis intensifies and fuel prices become increasingly volatile, renewable energy sources offer the precious hope of a secure and sustainable future. The sea waters surrounding the UK provide an abundant supply of both wind and marine power, which has driven rapid technical innovation in offshore energy systems as well as the emergence of a thriving industrial sector. As a result the UK is now one of the world’s largest markets for offshore wind, now accounting for up to 12% of the UK’s total energy use, and the country has become a global leader in the development of energy platforms that harness the natural power of the wind, the waves and the tides.
Despite such impressive progress, further expansion in the offshore renewables sector will be crucial for the UK to reach its target of achieving net-zero greenhouse gas emissions by 2050. That will require more scientists and engineers to have the skills and knowledge needed to design, build and operate offshore energy platforms that achieve efficient and reliable power generation without damaging the marine environment. Indeed, data collated by the consultancy firm PwC suggests that the number of jobs in the renewable energy sector is growing four times faster than the overall UK employment market, with advertised positions in the green economy almost trebling during 2022.
Developing such specialized skills is the prime motivation behind the UK’s only dedicated doctoral training programme in wind and marine energy. Bringing together leading research groups in offshore engineering at the University of Oxford, marine energy at the University of Edinburgh, and wind energy at the University of Strathclyde, the Centre for Doctoral Training (CDT) in Wind and Marine Energy Systems and Structures aims to equip its students with the technical knowledge and professional skills needed to drive future developments in this fast-growing sector. The four-year programme is supported by the Engineering and Physical Sciences Research Council and part-funded by a number of industrial partners.
According to the CDT’s co-ordinator, Drew Smith at the University of Strathclyde, around 70% of each year’s cohort move directly into the offshore renewables industry, with the remainder staying in the academic sector to pursue research into next-generation offshore energy systems.
Physics graduate Orla Donnelly says that the initial training year made her more confident about choosing her research topic, while also introducing her to other students and academics who are all working in the same area (Courtesy: Orla Donnelly)
“I knew I wanted to do a PhD, but I was also thinking about my future job options,” says Orla Donnelly, a physics graduate who is now in the second year of the programme. “In my final year I had a module in renewable energy that I really enjoyed, and the CDT seemed like an ideal opportunity for me to start building a career in the offshore energy sector.”
Since most students have very little prior knowledge of renewables technology when they enter the programme, in the first six months all new joiners complete a series of core modules at the University of Strathclyde – with topics ranging from aerodynamics and power conversion through to the safety, risk and reliability of offshore platforms. Students then have the option of taking three further taught modules during their first year, or starting their research project and then choosing another three modules later on in the programme.
Donnelly chose to devote her first year to the formal training, which provided her with a valuable insight into the different technologies involved in building and operating offshore energy systems. “When I started I really didn’t know enough about renewable technologies to know which area I wanted to focus on for my PhD,” she says. “The training year introduced me to the basics of wind, marine and tidal energy, and also allowed me to get to know the academic staff and their different areas of expertise. That made me much more confident about choosing my research project.”
Working through the core modules with students from different science and engineering backgrounds helps newcomers to get to grips with unfamiliar technologies, and to explore the wider economic and environmental factors at play. “We had 18 people in our year, including physicists and mathematicians as well as mechanical, civil and electrical engineers,” comments Donnelly. “We were able to help each other with our specialist knowledge, and that made everything much easier.”
The bonds forged between the students in that first year also generates a strong support network that persists throughout the CDT. “Most people think of a PhD as an individual endeavour, but I have become part of a large cohort of people who are all working in the same area,” continues Donnelly. “Our research projects may be focused on different problems, but we can still offer an opinion if someone runs into an issue.”
Jade McMorland, who is now in the final year of the CDT, has enjoyed the opportunity to discuss her research with different companies and academic groups in the offshore renewables sector (Courtesy: Jade McMorland)
Jade McMorland, who is now in her final year of the CDT, has also valued the collaborative nature of the programme. Her research project is focused on the operations and maintenance of next-generation wind turbines, including floating-wind designs that are being developed to enable energy platforms to be built in deeper, and therefore windier, waters. “When I first started there was only one other student who was working on floating wind, but now there are about 10 of us,” she says. “We set up our own research group, which has enabled us to do really fun things like data sprints on real-life operations. If I’ve got a question about something really specific, I know there will be someone in the group who has the specialist expertise to help me.”
McMorland has also been a prime mover in the Professional Engineers Training Scheme (PETS), a student-led initiative that aims to develop skills and competencies that would otherwise be difficult to acquire during a PhD project, such as team management and leadership skills. In large part that is achieved through an outreach programme that includes educational activities at local schools, networking events and seminars, and the organization of the CDT’s annual conference.
The PETS committee also oversees the professional training and skills development needed for students to achieve chartership status, which is a particular advantage for students who are keen to work in industry. “Through PETS and some additional training we try to fulfil all the main competencies needed for chartership,” says McMorland. “Feedback from our sponsored students and our industrial advisory board suggests that it is becoming more important to become a chartered engineer to progress quickly within the offshore renewables industry.”
As well as boosting the students’ career prospects, PETS plays an important role in strengthening the connections between cohorts and the three institutions that make up the CDT. The committee organizes social activities, operates a buddy system to allow newcomers to benefit from the experience of older students, and has a direct link into CDT management to provide a voice for the student community. “PETS was a big selling point for me with the CDT,” says McMorland, who chaired the committee last year and is now co-chair. “It’s nice to have an hour away from your research where you can just chat to other people about all the different activities they’re involved in.”
While many new graduates might be tempted by the immediate career opportunities available in such a buoyant industry, McMorland feels she has benefited from the experience of running her own research project in an environment that has enabled her to make lots of new connections.
“It has been great to explore an area, find a problem that is important to take forward, and delve deep into a topic that I’m really interested in,” she says. “Within a couple of months of starting my PhD I was in Denmark presenting my work, and I’ve really enjoyed the opportunity to engage with different companies in the offshore renewables industry and to attend conferences where other people are really interested in my research.”
• Applications for the CDT in Wind and Marine Energy Systems and Structures are now open for the academic year starting in September 2023. High-calibre candidates should have a first-class or upper second-class degree in mathematics or any scientific or engineering discipline, and must be able to demonstrate excellent maths skills.
