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Hunt for the superheavies

Atomic nuclei have been intensely researched for more than a century, but they remain things of mystery and wonder – especially to the nuclear physicists who study them. We know that nuclei are made of protons and neutrons bound together by the residual strong force. But the extreme difficulty of calculating nuclear properties using the Standard Model of particle physics leaves much to be learned about their internal workings. In a sense, nuclei are like the world’s oceans: despite their ubiquity, we are still on the shoreline trying to understand what lies in their depths.

Nuclei are made of just two components, but their properties can be very different indeed. Most of the nuclei in your body, for example, have been around for billions of years, yet some rare nuclei made in the lab can last just tiny fractions of a second before decaying. It is the heaviest of these rare nuclei, and the people who devoted their careers to discovering and characterizing them before they decay, that are the subject of Superheavy: Making and Breaking the Periodic Table by the pharmacist turned science writer Kit Chapman.

The book takes the reader on a romp that begins in 1930s Paris, when Irène and Frédéric Joliot-Curie discovered that heavier elements could be made by bombarding lighter elements with alpha particles (helium nuclei). This was followed shortly thereafter in Rome by Enrico Fermi and the “Via Panisperna Boys” who found that bombardment with neutrons had a similar effect.

The race was on to find new heavy elements and the result was a transformation of the periodic table – which is conveniently included in the frontmatter of Chapman’s book. Like many physicists, the last time that I had a serious look at a periodic table was when I took my last chemistry course – which was 35 years ago – and I rather sheepishly admit that studying the table once more was a revelation. Indeed, I wondered aloud “Where did all those new superheavy elements come from?” Even though as a physics journalist I have covered the twists and turns in the discovery and naming of new elements over the past two decades, I had always looked at each element in isolation and did not fully appreciate how the periodic table – full of holes when I was young – appears much more complete, at least for now.

What I mean by complete is that in the current incarnation of the familiar version of the table, the seventh and final row is full of elements named after people and places – there are no gaps and no systematic names such as unnilseptium that were placeholders as scientists argued over element names. The seventh row begins on the left with francium and radium; is punctuated by the 14 actinoids (from actinium to lawrencium); and then makes the sprint across the transition metals and on towards the noble gases.

The superheavy elements are the final 15 in this row, from rutherfordium with 104 protons, on to dubnium and eventually to oganesson with 118. Those last two names, by the way, reflect the importance of the Soviet/Russian Joint Institute for Nuclear Research (JINR) in the search for superheavy elements. The lab is in Dubna, near Moscow and since 1989 it has been run by Yuri Oganessian. Strictly speaking, new elements should not be named after living people, but two exceptions have been made – oganesson (118) and seaborgium (106), the latter honouring the nuclear chemist Glenn Seaborg, who created and ran the rare elements programme at the University of California, Berkeley.

GSI in Darmstadt, Germany, and RIKEN’s Radioactive Isotope Physics Laboratory in Japan were also major contributors to the discovery of the superheavy elements. They have been honoured with the names darmstadtium (110), hassium (108) and nihonium (113) – the last two inspired by the Latin name for the German state of Hesse and an alternative name for Japan.

Like many things in modern physics, the drive to create superheavy elements began in earnest during the Second World War with the race to build the atomic bomb – and specifically the development of a way to produce significant amounts of plutonium. That element was discovered in 1941 at the University of California Berkeley by a team that included three future Nobel laureates: Seaborg, Emilio Segrè and Edwin McMillan.

Chapman reveals that Seaborg chose the symbol Pu for plutonium because of the stench of his Berkeley chemistry lab. Although physicists had played an important role in the early discovery of new elements – the work of Seaborg and colleagues was made possible by the cyclotron, which was invented at Berkeley by the physicist and Nobel laureate Ernest Lawrence – it was chemists who isolated the new elements from bombarded targets. This was no mean feat; not only did they have to predict the chemistry of an element that had never been seen before, they also had to work very quickly because the elements have short half-lives. Indeed, Chapman tells us that Berkeley nuclear scientist Albert Ghiorso famously used a souped-up Volkswagen Beetle to transport samples in the shortest time possible across the campus, from where they were made to where they were analysed.

Because much of the early effort to create new elements occurred during the Second World War and the Cold War, there was a certain amount of censorship involved in publication of the work. Before the US entered the war in 1941, Chapman points out that the British were concerned that American scientists were providing the Germans with information that could be used to create nuclear weapons. In 1945 US officials prevented the publication of a Superman comic strip because the superhero was irradiated in a cyclotron – which was described with too much accurate detail for wartime censors.

While Seaborg is the scientist most associated with the discovery of new elements, it is Ghiorso who holds the record for being involved in the most discoveries. In 1993 he helped discover element 106, putting his tally at 11 and beating the 185-year record held by Humphrey Davy. Because the discovery was made at Berkeley, the lab gained the right to name the element. This was at a time when Berkeley, JINR and Darmstadt were in competition to find and name new elements.

The days of isolating new elements and studying their chemistry was waning. By the 1990s researchers often only caught fleeting glances of new elements and had to try to determine their decay chains – often only seeing part of the picture. Science is usually done incrementally with different labs contributing evidence that eventually adds up to a discovery – giving priority as to who made a discovery and who therefore had naming rights was a tricky business.

While this competition between labs resulted in a flurry of new elements, the labs were at loggerheads when it came to naming the new elements. This ruckus was dubbed the “Transfermium Wars”, with transfermium referring to elements beyond fermium (100). The wars ran for about 30 years, starting in the 1960s, and during this period three different elements had been named rutherfordium by different research groups and three different names had been proposed for element 102. What is more, two different names had been proposed to honour the Danish physicist Niels Bohr – bohrium and nielsbohrium – the latter favoured by the Germans who were concerned that bohrium could be confused with boron.

In 1986 the Transfermium Working Group was set up by the governing bodies of chemistry and physics (IUPAC and IUPAP respectively) to sort out the mess and after a decade-long slog it finally came up with a definitive list of names in 1997 – and bohrium (107) won out over nielsbohrium.

Atoms formed by superheavy elements have properties that are not predicted by their position in the periodic table

As for the future of the superheavy element hunters, Chapman writes that the best guess of physicists is that there could be as many as 172 elements – which means more than 50 could still be up for discovery. But Chapman also points out that discovering more and more heavy elements could be the undoing of the periodic table, bringing about the “end of chemistry”. While that might sound ominous, I’m afraid it doesn’t mean that chemistry students of the future can avoid learning how to balance redox reactions. What Chapman means is that the atoms formed by superheavy elements have properties that are not predicted by their position in the periodic table – a cornerstone of chemistry.

An early hint of this is that research using tiny numbers of copernicium (112) and flerovium (114) atoms at Dubna suggests that the element’s chemical properties are not as expected given its place in the periodic table. Flerovium, for example, should behave like lead, which is the element above it in the periodic table and copernicium should behave like mercury – but that is not what the study found. The likely reason is that these elements have huge charges on their nuclei and large numbers of electrons, so that conventional way of understanding how these elements react breaks down.

So rather than heralding the end of chemistry, the superheavy elements look set to open an exciting new chapter.

2021 Bloomsbury Sigma £10.99pb 304pp

A new approach to Hall measurement

This video highlights the MeasureReady M91 FastHall, a revolutionary, all-in-one Hall analysis instrument that delivers significantly higher levels of precision, speed, and convenience to researchers involved in the study of electronic materials.

The M91 FastHall measurement controller combines all of the necessary HMS functions into a single instrument, automating and optimizing the measurement process, and directly reporting the calculated parameters. With Lake Shore’s patented new FastHall measurement technique, the M91 fundamentally changes the way the Hall effect is measured by eliminating the need to switch the polarity of the applied magnetic field during the measurement. This breakthrough results in faster and more accurate measurements, especially when using high field superconducting magnets or when measuring very low mobility materials.

Tracking traffic patterns in the mouse brain

Allen Institute researchers (left to right) Greggory Heller, Tamina Ramirez, Corbett Bennett, Séverine Durand and Joshua Siegle) are using Neuropixels probes to reveal how visual information flows through the mouse brain. (Courtesy: Shawn Olsen)

The field of neuroscience has come a long way: beginning with single electrode electrophysiological recording of one neuron at a time and progressing to simultaneous recording of multiple neurons’ activity using tetrodes implanted in the brains of (typically) mice and monkeys. Today, advances in fluorescence microscopy and fluorescent protein engineering, combined with multielectrode recording, enable acquisition of the spatiotemporal details of electrical activity of neurons in vivo in real time.

In a recent study published in Nature, a team headed up at the Allen Institute went even further, recording the activity of hundreds of neurons at once to create the largest dataset of neurons’ electrical activity in the world.

Towards comprehensive mapping of brain activity

Joshua Siegle, Xiaoxuan Jia and colleagues took advantage of a previously developed technology called Neuropixels to achieve multichannel, large-volume, high-resolution spatiotemporal coverage of neuronal activity. Neuropixels is a silicon probe containing 384 recording channels; using only two probes, more than 700 well-isolated single neurons can be recorded simultaneously across different regions in the (mouse) brain.

The Allen Institute team, led by Shawn Olsen and Christof Koch, used Neuropixels to record activity from hundreds of neurons in up to eight different visual regions of the brain in awake, head-fixed mice viewing diverse visual stimuli. In contrast to sparse multichannel recording, localized large-volume coverage of several brain regions at once can reveal the information flow through the brain. In addition, capturing information from different areas in the brain simultaneously helps reveal how the brain operates through the interaction of these different areas.

Finding hierarchy during information processing

The team implanted Neuropixels probes up to 3.5 mm into the animals’ brains to measure responses from visual cortical (primary visual cortex and five higher cortical areas) and thalamic areas. During recording sessions, mice passively viewed a range of natural and artificial visual stimuli including drifting gratings and full field flashes. By measuring time delays in neuronal activity between different brain regions, as well as the size of visual field that each neuron responds to, the team observed that the information flow follows a hierarchical organization.

The researchers also carried out Neuropixels recordings in another set of mice that were trained to respond to a visual change. They found a similar hierarchical structure in activity during this behavioural task: neurons in visual areas higher in the hierarchy responded more strongly when the stimulus changed. The recordings enabled the researchers to infer the animal’s success in detecting a change in visual stimuli by just looking at the neuronal electrical activity. Interestingly, observing activity in the higher-order areas allowed the researchers to predict these successes with greater accuracy, suggesting that these areas are more likely to be involved in guiding behaviour.

In the absence of background light (removing the visual input from the mice), the same neurons still fired; however, the order of information flow was lost. This could mean that some sort of hierarchy is needed to process information and understand aspects of the world around us. Although mouse vision is not the same as humans, neuroscientists can still learn many working principles of sensory processing that are generalizable to how humans perceive and process information as some level.

“At a very high level, we want to understand why we need to have multiple visual areas in our brain in the first place,” says Siegle. “How are each of these areas specialized, and then how do they communicate with each other and synchronize their activity to effectively guide your interactions with the world?”

Qubit needle detected in a haystack of nuclear spins

Researchers at Cambridge University in the UK have found a new way to detect a single quantum bit (qubit) hidden in a dense cloud of 100 000 qubits made from the nuclear spins of quantum dots. The feat, which involves laser light and a single electron that acts like a spin-herding “sheepdog”, might aid the development of a quantum Internet.

Quantum computers can already outperform powerful supercomputers within a narrow range of highly specialized tasks. However, for quantum devices to reach their full potential, researchers need to find some way of networking them into a quantum Internet. One route being explored would involve storing quantum information in an ensemble of coherently interacting spins. Nuclear spins in semiconductor quantum dots – tiny pieces of semiconducting crystals that act like artificial atoms – are one promising possibility.

Hiding a qubit

The problem is that the quantum information stored in the nuclear spins of these dots – or indeed the spins of any other suitable material – is fragile. One way to overcome this is to protect the information-containing spins by “hiding” them in the cloud of spins from the 100 000 atomic nuclei within each quantum dot. An information-containing spin can then be thought of as a “needle” and the cloud of other spins as a “haystack”, explains team leader Mete Atatüre, a physicist in Cambridge’s Cavendish Laboratory.

Semiconducting quantum dots lend themselves to this type of subterfuge because researchers can inject a single nuclear spin that has been excited with laser light into an ensemble of nuclear spins in the dots. In the new work, the Cambridge team injected such a single nuclear excitation, known as a nuclear magnon, into dots made of indium gallium arsenide.

So far, so good. The real hurdle, Atatüre explains, came when he and his colleagues tried to sense the presence of the stored quantum information in the ensemble of spins. This proved difficult because the spins tend to “flip” randomly when addressed, creating a noisy system. The way they got around this challenge was to use a (proxy) electron in the material that acts “like a dog that herds sheep”, as Atatüre puts it. The sheep, in this case, are the ensemble of nuclear spins.

Collective nuclear spin excitation

In their experiments, the researchers measured the spin resonance frequency of their sheepdog electron with high precision using a laser technique known as Ramsey side-of-fringe. They then used this resonance frequency to detect the excitation state of an individual nuclear spin. The detection technique only works, however, if the chaotic ensemble of nuclear spins is first cooled down to ultralow temperatures (using another beam of laser light) so that the spins begin to act as a collective nuclear spin excitation — or spin wave – with a defined state.

Atatüre explains that this is because a single nuclear spin injected into a spin wave is far easier to pick out than a spin injected into a chaotic (non-cooled) ensemble of spins. “If we imagine our cloud of spins as a herd of 100 000 sheep moving randomly, one sheep suddenly changing direction is hard to see,” he says. “But if the entire herd is moving as a well-defined wave, then a single sheep changing direction becomes highly noticeable.”

Weak measurements track single nuclear spins

By controlling the collective state of the 100 000 spins, the researchers were able to detect the existence of the stored quantum information as a flipped qubit with a precision as high as 1.9 ppm. For their apparatus, this precision represents the fundamental limit set by quantum mechanics.

Having harnessed control and sensing in such a large ensemble of nuclei, the Cambridge team says it now plans to demonstrate storage and retrieval of a full-blown arbitrary quantum bit using its technique. “Being able to do this will allow us to overcome a major building block for the quantum Internet: a deterministic quantum memory connected to light,” Atatüre tells Physics World.

The present work is detailed in Nature Physics.

Deep learning enables safer heart scans with lower radiotracer dose

De-noising PET scans — Static cardiac ¹⁸F-FDG-PET images from a representative patient showing the effect of applying de-noising (AI_1% and AI_10%) to dose-reduced images (1% and 10%). A low-dose CT (LDCT) is shown for reference. (Courtesy: *Phys. Med. Biol.* 10.1088/1361-6560/abe225)

Positron emission tomography (PET) with the radiotracer ¹⁸F-FDG provides an important tool for assessing the health of the heart muscle in patients with ischemic heart disease, in which narrowed coronary arteries reduce the heart’s blood supply. Such PET scans help identify the level of damage to the heart muscle and play an important role in clinical decision making.

Current guidelines recommend injecting a 200–350 MBq dose of ¹⁸F-FDG. But lowering this tracer dose will decrease the patient’s radiation exposure – an essential goal of any diagnostic procedure – as well as reducing imaging costs and potentially opening up new applications. The downside, however, is that a lower tracer dose may lead to poorer quality images, thereby reducing diagnostic accuracy.

One approach proposed to address this problem is to employ artificial intelligence algorithms to restore image quality. Researchers from Rigshospitalet in Denmark have now investigated the use of deep learning to reduce noise in low-dose PET images. They validated the diagnostic accuracy of this approach using ¹⁸F-FDG images of patients with ischemic heart disease, detailing their findings in Physics in Medicine & Biology.

First author Claes Nøhr Ladefoged and colleagues retrospectively examined 168 patients referred for cardiac viability testing using ¹⁸F-FDG-PET/CT. Patients received approximately 300 MBq of ¹⁸F-FDG and one hour later underwent a low-dose CT scan followed by a thoracic PET scan.

The researchers reconstructed both static and ECG-gated (with eight gates) PET images. They also simulated dose-reduced images with 1% and 10% of the total counts, corresponding to tracer doses of 3 and 30 MBq, respectively. They then trained U-Net, a 3D convolutional neural network developed for biomedical image segmentation, to de-noise the four sets of dose-reduced PET images (static and gated data with the two dose reduction thresholds).

Clinical metrics

Diagnosis of patients with ischemic heart disease is based on several factors, including estimates of end-diastolic volume (EDV), end-systolic volume (ESV), left ventricular ejection fraction (LVEF) and FDG defect extent (deviation from inter-subject normal perfusion). Patients with normal myocardial perfusion usually have low extent scores and high LVEF, although there’s no specific threshold.

The researchers compared full-dose, dose-reduced and de-noised dose-reduced PET images from 105 patients. Using Corridor4DM software, which automatically segments the left ventricle, they extracted values of EDV, ESV and LVEF from the gated images, and FDG defect extent from the static images.

For EDV and ESV measurements, the full-dose and 1% dose-reduced PET images matched well, with a correlation coefficient of above 0.93, which increased to above 0.98 with de-noising. Significantly, for LVEF, de-noising increased this correlation from 0.73 to 0.89. In the 10% dose-reduced images, the team saw excellent correlation across all metrics with only minor improvements after de-noising. They note that none of the de-noised images were significantly different from the full-dose images.

The accuracy of diagnosis, based on European Society of Cardiology guidelines that define normal LVEF as 50% or above, improved after de-noising the dose-reduced images. When using the 1% dose-reduced images, 13 patients had a different diagnosis to that suggested by the full-dose measurement. De-noising improved this to just two patients. For the 10% dose-reduced images, five patients had discordant diagnosis before de-noising and all diagnoses agreed after de-noising.

The researchers note that the FDG defect extent score was, on average, only moderately affected by the dose reduction, with even the 1% dose-reduced images providing similar scores to the full-dose images. This is likely because this metric is measured from static PET images, in which all true coincidence events are used. In contrast, ESV and EDV measurements are taken from gated PET images, which only include one eighth of the counts in each gate, resulting in greater noise.

The reduced-dose images also exhibited a marked improvement in image quality after de-noising. Comparing standardized uptake value (SUV) measurements for the 1% dose-reduced and the full-dose static images showed considerable bias in the dose-reduced images. After de-noising, however, they exhibited near-identical SUV. SUV in the 10% dose-reduced images largely resembled those of the full-dose images, but were further improved using the de-noising model.

The researchers conclude that their deep-learning noise-reduction model enables significant ¹⁸F-FDG dose reduction in cardiac PET imaging without losing diagnostic accuracy. “A reduction to one hundredth of the dose is possible with quantitative clinical metrics comparable to that obtained with a full dose,” they write. “This dose reduction is important for patients, staff, general radiation protection and healthcare economy.”

Plasmonic metasurface gives high-speed optical WiFi a boost

Physicist and engineers at Duke University in the US have developed a new metamaterial that could substantially increase the speed of wireless optical communications. The material, which consists of an array of “nanoantennas” made from cubes of silver just 60 nm wide, can capture light within a 120-degree field of view and relay it into a narrow angle with a record-high efficiency of around 30%.

Although light in the visible and infrared part of the electromagnetic spectrum carries more information per unit time than the radio waves used in wireless technologies such as Bluetooth and WiFi, data transmission at visible and infrared wavelengths is currently restricted to fibre-optic cables. One reason for this is that wireless receivers must be able to capture light from different directions simultaneously. The simplest way to do this is to make the receivers physically bigger, but that reduces the speed at which they can transmit information onwards, thus lessening any advantage.

In 2016, researchers at the Connectivity Lab (a subsidiary of Facebook) developed a new type of receiver that could, in principle, be used for wireless communications at optical frequencies. Their device consisted of a spherical bundle of fluorescent fibres that captured blue light and re-emitted green light that could then be funnelled into a small receiver. However, it could only transmit two gigabits (Gb) of information per second, which compares poorly with standard fibre-optic providers (which typically offer around 10 Gbs) as well as high-end systems offering 1000s of Gbs.

Speeding up

A team led by Maiken Mikkelsen has now used the physics of surface plasmons to speed up the Connectivity Lab’s design. Plasmons are quasiparticles that arise when light interacts strongly with electrons in a nanostructured metal, causing the electrons to oscillate collectively. By adjusting the shape, size and arrangement of the nanoscale structures, the metallic material can be tailored to capture light at specific frequencies, increasing the device’s light-absorbing speed and light-emitting efficiency by a factor of more than 1000.

Mikkelsen and her colleagues made their plasmonic metasurface by depositing an array of silver nanocubes, spaced 200 nm apart, atop a thin (75 nm) silver substrate coated with a polymer containing four layers of fluorescent dye. The researchers report that the interaction of the nanocubes with the electrons in the substrate 7 nm below enhances the overall fluorescence of the dye by 910 times and its light emission rate by 133 times. Such values were previously only possible for isolated, highly optimized single nanostructures, not for whole arrays. “While we haven’t yet integrated a fast photodetector like the Connectivity Lab did in their original work, we have solved the major bottleneck in the design,” Mikkelsen says.

Centimetre-sized sample

The researchers also observe that the metasurface can collect fast-modulated light with a 3 dB bandwidth exceeding 14 GHz from a 120-degree field of view and relay it into a narrow angle with an overall efficiency of around 30%. This value, they say, is a record high “to the best of our knowledge”.

The researchers, who describe their experiments in Optica, say they can fabricate their metasurface over areas as large as centimetres using a simple technique known as liquid deposition without any loss in efficiency. They now plan to assemble several plasmonic devices together to cover a 360° field of view.

Light-induced lattice vibrations could speed up data recording

magnet's crystal lattice — The researchers used ultrashort laser pulse excitation to optically stimulate specific atomic vibrations of the magnet’s crystal lattice. (Credit: Lancaster University)

Intense laser pulses can turn an antiferromagnetic material into a ferromagnetic one within just a few picoseconds (10^-12 s) – a time scale that matches the fundamental limit for magnetization switching and vastly exceeds the recording speeds of today’s computer hard drives. The technique, which works by optically “shaking” the crystal lattice of dysprosium orthoferrite (DyFeO₃), could form the basis of a fast and energy-efficient new way of processing data.

Modern hard disk drives encode data by using magnetic field pulses to flip the spins of electrons (representing binary zeros and ones) in ferromagnetic materials within the disk. Because these magnetic pulses require a substantial electrical current, the data-writing process dissipates significant amounts of energy. It is also relatively slow, with a complete spin flip taking tens of nanoseconds (1 ns = 10^-9 s).

Antiferromagnets like DyFeO₃ are considered promising candidates for future high-density memory applications because their spins flip much faster, with characteristic frequencies in the terahertz range. These rapid spin flips are possible because the electron spins in DyFeO₃are aligned antiparallel to each other – meaning that the material (unlike ferromagnets, which have parallel electron spins) lacks a net magnetization. The spins in antiferromagnets are also robust to external magnetic perturbations, making them a stable platform for data storage.

Controlling the exchange interaction

Researchers led by Andrea Caviglia of the Delft University of Technology in the Netherlands have now put these properties to work by showing that intense (> 10 MV cm^–1) mid-infrared laser pulses just 250 femtoseconds (1 fs =10^-15 s) long can switch the spins in DyFeO₃ in less than 5 picoseconds. The mechanism for this switch lies in the interaction between an electron’s spin (roughly, its rotation on its own axis) and its orbital momentum, which stems from the electron’s movement around the atomic nucleus and is related to the shape of the material’s electronic orbital.

In DyFeO₃, the spin of the transition-metal (Fe) ion and the orbital momentum of the rare-earth (Dy) ion are strongly coupled via a mechanism known as an exchange interaction. This quantum interaction occurs between pairs of identical fermions (such as electrons), and it tends to prevent the spin magnetic moments of neighbouring fermions from pointing in the same direction.

Caviglia and colleagues, however, found that the intense laser pulses essentially “shook up” the lattice of DyFeO₃, producing ultrafast and long-lasting changes in the exchange interaction. These changes made it possible for the material to undergo a phase transition, switching from an antiferromagnet to a ferromagnet.

Ultrafast lattice control

The researchers, who report their work in Nature Materials, say that it was previously thought that phonons (that is, vibrations) could only change a material’s magnetism on a timescale of nanoseconds. “We have reduced the magnetic switching time by a 1000, which is a major milestone in itself,” says team member Rostislav Mikhaylovskiy of Lancaster University in the UK.

The researchers hope that their findings will encourage further research into the exact mechanisms governing ultrafast lattice control of magnetic states. They now plan to optically stimulate other phonon modes in DyFeO₃. “These modes often feature a symmetry that is different to the one we have already addressed and thus might have a fundamentally distinctive impact on the magnetic state of the antiferromagnet,” study lead author Dmytro Afanasiev tells Physics World. “Who knows what kind of novel scenarios for light-driven magnetic recording they may provide.”

Dress inspired by Perseverance Rover’s parachute, augmented reality Sun brightens your living room

“Dare mighty things” was the message surreptitiously encoded into the parachute of NASA’s Perseverance Rover, which landed on Mars last week. Now, designers at Svaha Apparel have created a dress based on the pattern of red, white and black segments that made up the parachute. The company is currently running a pre-order campaign and says that it will produce the dress is if gets at least £10,000 worth of orders. According to the Svaha website, the goal has already been met – so the dress may soon be available for $69.99. The company is running a similar campaign for a parachute-inspired t-shirt, which retails for $24.99.

In 2003, the Danish-Icelandic artist Olafur Eliasson lit up the Turbine Hall of London’s Tate Modern with an artificial Sun. Now you can brighten up a room in your house on a dull winter’s day with a virtual version of that artwork – at least when you look at the room through the camera of your smartphone.

Eliasson has teamed up with Daniel Birnbaum, director of the augmented reality platform Acute Art to create a Pokemon Go-like version of his Sun that appears on your screen. And if that gets too bright for you, a rain cloud is available – perhaps followed by a virtual rainbow.

Shapley, Curtis and the ‘island universes’ controversy

“The Shapley–Curtis debate makes interesting reading, even today. It is important not only as a historical document but also as a glimpse into the reasoning processes of eminent scientists engaged in a great controversy for which the evidence on both sides is fragmentary and partly faulty. This debate illustrates forcefully how tricky it is to pick one’s way through the treacherous ground that characterizes research at the frontiers of science.” – Frank Shu

In 1919 George Hale, head of Mount Wilson Observatory, called for the US National Academy of Sciences to host a debate about either Einstein’s theory of relativity or “island universes” – galaxies outside of our own. The home secretary of the academy, C G Abbot, was sanguine that either would be worth pursuing on a public stage. He wrote to Hale saying: “You mentioned the possibility of a sort of debate. From the way the English are rushing relativity in Nature and elsewhere, it looks as if the subject would be done to death long before the meeting of the academy, and perhaps your first proposal to discuss the island universe would be more interesting. I have a sort of fear, however, that people care so little about island universes that unless the speakers took pains to make the subject very engaging, the thing would fall flat.”

And so it followed that at a meeting of the academy on 26 April 1920, scientists Harlow Shapley and Heber Curtis presented contrasting arguments that collectively came to be known as “the Great Debate”, though at the time it was officially titled “The Scale of the Universe”.

Shapley argued that there was nothing more to the universe than our Milky Way galaxy, and there were no other “island universes”. He could not swallow the notion that there was more to reality than our own galaxy, as that would imply that Andromeda (pictured above) was about 10⁸ light-years away from us. Furthermore, he claimed these observed “spiral nebulae” were merely nearby gas clouds within the Milky Way, rather than distinct galaxies in their own right. He also argued that our Sun was far from the centre of the Milky Way, yet another point of disagreement between Curtis and him.

The Great Debate was not only about the nature of the universe. The young, hungry Shapley had an agenda – he had hoped that by defeating the older Curtis, he would earn the directorship of Harvard College Observatory. It would be a tall order – Curtis had been known to be a skilled and precise orator. And his confidence was on full display even before the debate. In a letter to Shapley he wrote that “A good friendly scrap is an excellent thing, once in a while…sort of clears up the atmosphere.”

A good friendly scrap is an excellent thing, once in a while…sort of clears up the atmosphere

It is likely that Shapley knew he would be swimming upstream. He opened his argument by saying that “To Ptolemy and his school, the universe was geocentric; but since the time of Copernicus the Sun, as the dominating body of the solar system, has been considered to be at or near the centre of the stellar realm. With the origin of each of these successive conceptions, the system of stars has ever appeared larger than was thought before. Thus the significance of man and Earth in the sidereal scheme has dwindled with advancing knowledge of the physical world, and our conception of the dimensions of the discernible stellar universe has progressively changed. Is not further evolution of our ideas probable?”

Contrary to Shapley, Curtis argued that Andromeda and other spiral nebulae could, in fact, be other galaxies. In support of his hypothesis he appealed to the fact that Andromeda seemed to possess more novae than the Milky Way. Why would this be if Andromeda was merely a part of the Milky Way? A better explanation was that Andromeda was a distinct galaxy that simply possessed a different rate of nova occurrences than the Milky Way.

Shapley and Curtis were both given 40 minutes to make their case to an audience of academics, possibly including Albert Einstein. Shapley presented ideas he had written in one of his papers, emphasizing the scale of the Milky Way. Curtis, meanwhile, offered a slideshow to express his explanation that spiral nebulae were actually “island universes” – better known to us today as galaxies. The speakers were not really addressing each other’s core arguments, with Shapley focusing on the Milky Way’s size and Curtis on the possibility of island universes. Curtis’s eloquence and stage presence dwarfed Shapley’s, which may ultimately have contributed to Curtis’s victory in the eyes of the audience.

Fortunately for Shapley, he still earned the directorship of the Harvard College Observatory, while Curtis went on to run the Allegheny Observatory. In 1923 astronomer Edwin Hubble measured the changing brightness of what are called Cepheid variable stars. He demonstrated that they were so distant from us as to be outside of the Milky Way. With that, the Great Debate was settled, and Curtis’s apparent victory upgraded to a definitive one.

Shapley’s position that the Milky Way is the entirety of our universe might seem laughable to our contemporary minds. No modern scientist would admit to ever rejecting a good explanation of observations merely because it violates our intuitions about what reality should be like. But we should hesitate before judging Shapley. Today, there are debates about the existence of the multiverse, and future scientists may one day laugh at our unwillingness to accept that, just as we are tempted to judge Shapley’s resistance to accept the true size of the universe.

This article was published in Lateral Thoughts, Physics World’s regular column of humorous and offbeat essays, puzzles, crosswords, quizzes and comics, which appears on the back page of the print edition. You can submit your own Lateral Thoughts. Articles should be 900–950 words, and can be e-mailed to pwld@ioppublishing.org

COVID-19 leads to major overhaul for radiotherapy

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Greater use of hypofractionated dosing regimens has helped radiation oncology sites deliver radiation therapy to cancer patients in England during the COVID-19 pandemic, offsetting a massive decline in treatment sessions overall, according to a study published in Lancet Oncology.

The study from the University of Leeds with Public Health England and the Royal College of Radiologists evaluated how radiation therapy practice changed on a number of fronts during the first wave of the outbreak.

Compared with the same periods in 2019, in 2020 the number of radiotherapy courses dropped by 19.9% in April, 6.2% in May and 11.6% in June, reported Katie Spencer, a fellow in clinical oncology at Leeds Teaching Hospitals National Health Service (NHS) Trust, and colleagues. The data reflect guidelines during the pandemic and more appropriate use of radiation therapy in some key areas, such as short courses with high doses (hypofractionated) where appropriate, delays for nonurgent care, and increased use of radiation therapy as an alternative to surgery.

“Although radiotherapy activity decreased during the first wave of the pandemic, our data suggest that the overall impact of this decline is likely to be modest,” said the group. “In addition, radiotherapy appears to have mitigated against some of the indirect harms of the pandemic by maintaining curative treatment options despite the challenges facing surgical services.”

Search for value in cancer care

Spencer is a specialist on health economics and value in cancer care, particularly the use and cost-effectiveness of radiotherapy, and an experienced user of routine NHS healthcare data to understand variation and improve value and outcomes. Her team’s study was designed to evaluate the impact of the COVID-19 pandemic on radiotherapy services across the NHS in England and guidelines issued in response to the outbreak. About one-third of cancer patients typically undergo radiation therapy.

Katie Spencer. (Courtesy: University of Leeds)

“Alongside surgery and systemic anticancer therapy, radiotherapy plays a major part both as a curative treatment and in the palliation of [localized] symptoms from advanced disease,” the authors wrote. “At the outset of the pandemic, all three treatment modalities were affected by constraints on COVID-19 testing and staff shortages.”

Researchers evaluated the use of radiation therapy delivered by all 52 NHS radiation therapy providers in England pre-pandemic and through the end of June 2020. During a lockdown period – from 23 March to 28 June – the total number of radiation treatment courses dropped by 3263 across the NHS in England, while the number of treatment appointments was down by 119,050, the authors reported.

The declines were in line with national and international guidelines for prioritizing/triaging patients and managing care during the pandemic.

“The disproportionately greater fall in treatment attendances largely reflects a rapid increase in the use of ultra-hypofractionated treatment regimens across several [tumour] sites,” the authors noted.

For example, in April 2020, researchers reported dramatically more use of a treatment regimen that specified 26 Gy in five fractions for the neoadjuvant treatment of breast cancer, as opposed to the 40 Gy in 15 fractions that was more common pre-pandemic.

“A marked increase in the use of ultra-hypofractionation in the neoadjuvant treatment of rectal cancer was also observed, with a reduction in the use of less than 2 Gy per fraction regimens,” they said.

Other key findings

The researchers also reported that compared with other age groups, they found more of a decline in treatment for people over the age of 70, which could reflect higher risk of the patients due to age and comorbidities, as well as the ability to defer care for certain conditions such as prostate cancer and nonmelanoma skin cancer.

In tumour types that typically require more immediate treatment, such as cancers of the rectum, bladder and oesophagus, the researchers observed an increase in the number of treatment courses. Spencer and colleagues suggested that this could signal the use of radiation therapy as an alternative to surgery. For example, the number of curative courses for bladder cancer rose by 143.3% in May 2020 relative to May 2019.

Areas of concern, however, include a decline in the number of palliative treatment courses and a persistent decline in radiation therapy overall in June 2020 relative to June 2019. NHS data show that the number of referrals for possible symptomatic cancer was 21% lower in June 2020 compared with the same period in 2019, the authors noted.

“New diagnoses were suppressed by 26%, which is probably a key contributor to the ongoing suppression in radiotherapy activity up to June 2020,” Spencer and colleagues wrote.

It’s possible that this trend will have an effect on outcomes as the data are followed over time.

“As COVID-19 cases again rise, these data are crucial for modelling indirect harms of the pandemic and establish a new baseline for radiotherapy treatments from which to plan for the ongoing delivery of care throughout subsequent pandemic waves and into the recovery beyond,” the authors wrote. “They also reinforce the need to address any persisting delays in cancer diagnostic pathways.”

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