Nobel disciplines: this infographic shows all physics Nobel prizes in terms of subject area. Click to enlarge.(Courtesy: IOP Publishing)
We are getting excited here at Physics World because on Tuesday 5 October, the Nobel Prize for Physics will be announced. I have been writing about the physics Nobels for 15 years and now – as ever – I can honestly say that I have no idea who is going to win. And I am very happy about that.
For me, this uncertainty is the most exciting thing about the Nobel prize. There is no public shortlist and no-one except for the Nobel prize committee members has any clue about who will be getting the telephone call from Stockholm next Tuesday morning. What is more, nominations for the prize are kept secret for 50 years so it is impossible to know who has been in the running recently.
If you are interested in how the committee makes its decision – and the veil of secrecy surrounding it – check out this article I wrote about Lars Brink, a Swedish particle theorist who served on the Nobel Committee for Physics on eight separate occasions.
Bolts from the blue
For me, some of the most memorable prizes have come as bolts from the blue. These can be awards honouring important work that was done a very long time ago and all but forgotten by most Nobel pundits. My favourite example is the 2009 prize shared by Charles Kao, Willard Boyle and George Smith for work done in the 1960s on technologies that eventually made the Internet possible.
I also find it very exciting when the prize is given for recent work, which can equally come as a surprise. Indeed, just one year later in 2010, Andre Geim and Kostantin Novoselov were honoured for their isolation of graphene, which they did in 2004. Novoselov was just 36 when he bagged his prize, compared to Boyle who was 85.
Only once in the past 15 years have I predicted the Nobel winners. That was in 2013 when François Englert and Peter Higgs shared the prize for their theoretical prediction (made in the early 1960s) of the existence of the Higgs boson. That was an easy one because the Higgs boson was finally discovered experimentally at CERN in 2012 and it would have been a travesty if Englert and Higgs had not been honoured promptly.
Looking for patterns
Several years ago, I thought that I could improve my predictive powers by looking for patterns in how physics disciplines are favoured by the Nobel committee. As a guide, we produced the above infographic, which shows both the prevalence and chronological order of prizes in seven disciplines – and you can see the updated version above.
To me, the most striking recent feature in the infographic is the dominance of astronomy, astrophysics and cosmology prizes in the past decade. There have been four prizes in this discipline since 2011, with two in the past two years. The next most popular discipline is nuclear and particle physics, with two prizes in the past decade.
Since its inception in 1901, 11 Nobel prizes have been awarded (at least in part) in astronomy, astrophysics and cosmology. The first was in 1936 when Victor Hess shared one half of the prize for his discovery of cosmic rays. It took more than 30 years for the next prize to come round, which was bagged by Hans Bethe in 1967 for his work on nuclear reactions in stars. The 1970s, 1980s and 1990s saw at most two prizes per decade and it was not until the 21st century that numbers started to pick up.
Precision cosmology
Of these recent awards, I find the 2019 prize the most telling. Half of the award went to James Peebles for his theoretical work in cosmology. Peebles is celebrated for forging links between what had been the highly speculative world of cosmology and the increasingly precise observations of the universe being made by astronomers. This ushered in the era of “precision cosmology” whereby physicists have already made great strides in understanding the origins and nature of the universe.
The second half of the 2019 prize was shared by Michel Mayor and Didier Queloz for their discovery of the first known planet orbiting a Sun-like star. That discovery was made in 1995 using exquisitely precise observational techniques, which astronomers continue to improve on. So, if I am going to make a prediction, I would say to expect more Nobel prizes related to precision measurements of the cosmos.
Physics World‘s Nobel prize coverage is supported by Oxford Instruments Nanoscience, a leading supplier of research tools for the development of quantum technologies, advanced materials and nanoscale devices. Visit nanoscience.oxinst.com to find out more.
As scientists, one of the most frustrating things we can be told is “nice idea, but the technology to achieve it doesn’t exist yet”. Academic researchers rarely have enough time and resources to push the development of such technology forward, so these ideas invariably get shelved.
One such nice idea would be to use mass spectrometry to “see” metabolism – the chemical processes that underpin life itself – as they take place, to help our understanding of diseases. As you might imagine, the technology to do this doesn’t yet exist. But for once, a team of physicists, to which we belong, has been given both the time and resources to try and change that.
Mass spectrometry – where a sample is ionized to separate its components and measure them, based on the combined masses of its atoms – is one of the most sensitive and versatile techniques for studying the nature and interactions of molecules in a biological sample. The use of this century-old technique for biological applications has grown exponentially over the last 20 years, thanks to the discovery of “soft” ionization techniques, which allow researchers to analyse much bigger molecules than was ever possible before. Combined with the use of today’s improved computational power, mass spectrometry is now able to study everything from antibodies to viruses. Indeed, it allows researchers to identify, characterize and quantify proteins and other molecules present in biological samples.
Instrumental imagers Felicia Green (left) and Anna Simmonds are part of a team at the Rosalind Franklin Institute that is developing a novel mass spectrometry instrument. (Courtesy: Rosalind Franklin Institute)
Our team, based at the Rosalind Franklin Institute in the UK, is primarily interested in two areas of mass spectrometry: mass spectrometry imaging and structural mass spectrometry. Mass spectrometry imaging allows images of biological tissue samples to be produced by collecting mass spectra in a spatially resolved manner. Structural mass spectrometry methods make the technique increasingly useful for studying the structure of biological molecules, not just their identity. However, to study everything that is happening in a biological tissue sample at the molecular level at one time requires a degree of complexity that isn’t currently possible.
What we need is the ability to measure things at a systems level, to see all the molecules in one place, even in something highly heterogenous, like a tumour sample. The goal is to be able to measure and identify all the metabolic substances, the lipids and many of the proteins, in their original spatial location. This would create a complete picture of metabolism in situ, alongside the key proteins that govern that metabolism at a cellular level. If specific molecular interactions can be related to a disease state, it could make a fundamental impact on our understanding of diseases and how they might be treated.
Setting the challenge
Our team, led by analytical chemists Josephine Bunch and Zoltan Takats, has set itself quite a challenge: to develop new mass spectrometry instrumentation that can make molecular maps of biological tissues at unprecedented sensitivity, chemical depth and spatial resolution.
To do this, we are tackling the three Achilles heels of mass spectrometry for biological imaging: size of molecules, speed and molecular identification. The goal is to be able to study both large and small molecules using the same instrument, while also making measurements faster and increasing their sensitivity. And not just that: the machine will also need to have subcellular spatial resolution and swiftly identify the structures of all species detected.
We are tackling the three Achilles heels of mass spectrometry for biological imaging: size of molecules, speed and molecular identification
As a first step, the various groups involved in the biological mass spectrometry project have, with industry partners, been developing instruments that use new technologies – such as a new type of ion source – and combining existing technologies for the first time. The goal set by the Franklin for technology development is to improve by a factor of 10 on what’s currently possible – but in reality, we’re looking at much more than that just for these initial individual instruments. If we are finally able to combine them all into one mass spectrometer, it’s almost impossible to calculate quite how extraordinary that could be. Even if, ultimately, creating that one mass spectrometer with all these capabilities just isn’t possible, those individual improvements we will have made in sensitivity, image resolution, ion mobility resolution, mass accuracy, mass resolution and speed will still have wide-ranging benefits.
Shape and structure
One of the planned instruments is a hybrid that incorporates two mass analysers, a time-of-flight (TOF) analyser and a Fourier-transform ion cyclotron resonance (FT-ICR) analyser. The team working on this brings together scientists from our institution, along with those from the National Physical Laboratory and Imperial College London in the UK, as well as the global analytical instrumentation company Bruker. This hybrid instrument is being developed in parts, with the team currently spread across three locations and two countries. Ensuring that each piece works well independently is important, but we also have to make sure that all the pieces will fit together when we start to combine them, so we’re in frequent communication with each other to share our progress and ideas.
The high throughput of the TOF analyser in the hybrid instrument allows the rapid spectral acquisition necessary for high spatial-resolution MSI experiments, while the FT-ICR allows unparalleled mass resolution and access to many ion-manipulation techniques that will make it possible to probe the structure of biological molecules, not just their identity. The instrument will also include a tandem trapped-ion mobility spectrometry (TIMS) device, which can in addition analyse the structure of biomolecules as well as separate out the components of biological samples based on their shape (Analyst143 2249). We are currently working on modelling multiple possible geometries of the device, to explore how ions travel through it, as well as studying how the device would be able to direct ions into either one of the mass analysers.
1 The hybrid imaging instrument A schematic of the hybrid mass spectrometer, including a multimodal ion source, a tandem trapped-ion mobility spectrometry device and both a time-of-flight mass analyser and a Fourier-transform ion cyclotron resonance mass analyser. (Courtesy: Rosalind Franklin Institute)
To generate ions from biological samples, we are also designing a multimodal imaging source that will be coupled to the hybrid mass spectrometer. This source will include multiple ionization techniques to provide choice and flexibility over a number of aspects, including the pixel size of the resultant mass spectrometry image; which classes of biomolecules are ionized; and how much preparation needs to be performed on the sample prior to its analysis. We still need to make significant improvements to obtain the required sensitivity, while at the same time producing data that can be interpreted. With this in mind, we’re planning to include post-ionization techniques to increase the number of molecules detected from each sampling location, as well as to improve the range of biomolecules detected from tissues.
A prototype of the multimodal ion source has been developed and installed on a Bruker timsTOF fleX mass spectrometer. The current iteration of this ion source includes atmospheric pressure “matrix-assisted laser desorption/ionization” (MALDI) – an ionization technique that uses a laser-absorbing matrix to create ions from molecules, with minimal fragmentation – in both transmission and reflection modes. The set-up has successfully demonstrated an enhancement of detected ion intensity, by plasma post-ionization (Analytica Chimica Acta1051 110). This set-up has the ability to complement the molecular information collected by commercially available MALDI systems, by allowing a number of different chemical components to be analysed.
We currently use in-house software to control the source, which allows real-time processing of data to create a live mass spectrometry image, as the data are being acquired. It also provides feedback control of experimental parameters in an on-the-fly manner. As the software is highly modular, it will allow us to easily incorporate new additions, as the instrument evolves. Work is also under way on a new atmospheric-pressure interface that will improve the transmission of ions from the multimodal ion source into the mass spectrometer. Traditional interfaces are based on simple capillaries, which tend to have significant transmission losses when transporting ions and charged clusters into vacuum. By exploring novel inlet designs, we aim to create a new inlet that is customisable to each mode of the source, thereby significantly increasing our transfer yields, and improving the overall sensitivity of the set-up.
Protein problems
Analysing proteins, in particular, using mass spectrometry imaging is a key challenge for scientists, as proteins are often large and challenging to extract from biological samples. “Bottom-up” techniques aim to study proteins by digesting them (almost always enzymatically) into smaller fragments, which can then be “reconstructed” into the original protein. Unfortunately, these techniques often use liquid-phase reactions (such as “liquid chromatography” – a technique used to separate and analyse a mix of proteins) that are incompatible with mass spectrometry imaging, and require significant sample preparation and time.
With this in mind, we have developed an “atmospheric pressure glow discharge device” that can digest proteins and other large molecules in situ. A glow discharge is a plasma that forms when an electric current flows through a gas; and such plasmas have long been used as ionization sources in mass spectrometry. By developing this device, we aim to produce unique, consistent and spatially resolved markers from proteins, which could be subsequently analysed by mass spectrometry imaging. This would represent a dramatic reduction in sample preparation and, crucially, would retain the valuable spatial information in native samples. Another mass spectrometer we have planned will exploit new developments in the use of water cluster beams for molecular desorption, which can enhance sensitivity 100-fold while reducing and controlling the fragmentation during surface sampling. It will help us to retain sensitivity at very low pixel sizes and ensure full coverage across the types of biological molecules detected.
Snapshot in time
Yet another instrument we’re developing as part of the theme will use mass spectrometry in “microscope mode” and is based on secondary-ion mass spectrometry (SIMS), in which the specimen’s surface is sputtered using a focused primary ion beam, and the analysis is done by collecting ejected secondary ions.
Joint endeavour The stigmatic SIMS at the first stage of the build, including the C60+ primary ion gun and chamber of the instrument, installed at the University of Oxford. (Courtesy: Rosalind Franklin Institute)
Our “stigmatic” (microscope) SIMS instrument allows for rapid molecular mapping of biological tissues at unprecedented speed, as it decouples acquisition time from spatial resolution. Typically, mass spectrometry imaging works by scanning across a surface, and taking a mass spectrum at each spot, to build up the pixels of the image. In this case, however, the whole surface is imaged simultaneously using state-of-the-art cameras that operate as an array of position- and time-sensitive detectors, recording a mass spectrum for each pixel in the camera image (Rapid Commun. Mass Spectrom.27 2745).
This instrument design is a joint endeavour between the Franklin, chemists at the University of Oxford and staff from the ion-beam technology company Ionoptika. The ion source was built, tested and installed at Oxford by Ionoptika. Typically, SIMS is used for microprobe analysis, which uses a highly focused (~500 nm) primary ion beam, so the next stage required us to produce a uniform defocused beam (~2 mm) for microscope mode. This involved detailed modelling and simulation of the primary ion dynamics, and experimental measurement to ensure beam size and uniformity at the sample, before we could consider secondary ions and imaging. The Oxford team’s expertise in adapting complementary metal oxide semiconductor (CMOS) sensors into pixelated time-sensitive cameras (Phys. Chem. Chem. Phys. 16 383) will allow us to develop spatially sensitive detection systems that record the arrival position and time of each secondary ion with nanosecond timing resolution. By combining new ion beam technology (J. Am. Soc. Mass Spectrom.31 1903) and fast detectors, our team aims to improve both mass and spatial resolutions while maintaining rapid imaging. This would mean a mass spectrometry image of a standard tissue biopsy would take seconds rather than hours or days, paving the way for routine analysis.
The next stage of development will take place at the Franklin’s new hub building, which opened on the Harwell Campus near Oxford this year. The Franklin’s mission is to develop new technologies that can have a major impact on the life sciences, by pushing the boundaries of physical sciences. The building has been designed to house the new technologies being developed under each of the institute’s key research areas – which include artificial intelligence and structural biology, among others – as well as providing space for the teams to work together on further innovations. Bit by bit, we’ll be moving our novel instruments, developed at different sites around the UK, into their new home. Then we’ll need to see if we can combine them all together, turning that “nice idea” into reality.
Elastomers that undergo large spectral shifts in colour when stretched very little have been developed by researchers in the US and South Korea. The material scientists say that these liquid crystalline elastomers with an unusually large Poisson’s ratio could have a variety of uses, from visual displays to smart windows.
Colour can be produced by the absorbance of light by dyes and pigments. Any wavelengths not absorbed reflect back and create the colour that we perceive. But colour can also be produced by nanoscale structures that scatter and reflect light. Indeed, such structural colours represent some of the brightest colours in the natural world.
There has been a lot of research interest in creating structural colours. As well as having the potential to be brighter, they offer other advantages over dyes and pigments. The nanostructures are more robust and longer lasting, and scientists claim they could be more environmentally friendly. They can also be engineered to scatter non-visible light, with reflection of infrared light having potential applications for passive cooling.
One challenge that material scientists have struggled with, however, is creating structural colouration that can change colour. One way to do this is to mechanically deform the material. The problem with this approach, says Shu Yang, an engineer and materials scientist at the University of Pennsylvania, is that you have to stretch it a lot. To shift from red to blue you would need to stretch the typical liquid crystal elastomers used by at least 40%, and in some cases by as much as 70%, she explains.
Now, Yang and her colleagues have managed to create an elastomer that can colour shift from near-infrared to ultraviolet wavelengths when stretched by less than 20%. They describe their work in Nature Materials.
Pressure-activated displays
To create structural colour, the team used chiral nematic liquid crystalline elastomers. When these elastomers are produced, a chemical dopant encourages the molecules to form helixes. It is these helixes that create the structural colour, with the wavelengths reflected dependent upon their dimensions. If the material is stretched, the helixes compress and the material’s colour changes.
Yang tells Physics World that when one of her colleagues was playing around with the production of these liquid crystalline elastomers to improve the uniformity of the helixes and therefore the colour, they managed to produce a very soft material. It turned out that the elastomers the team created had an unusually large Poisson’s ratio. This means that when you stretch them in one direction, they compress much more than you would expect in the other plane. “That is why we are able to have a very large wavelength change at a small strain,” Yang says.
Next, the researchers used the elastomers to create pneumatically actuated displays. They 3D printed a plastic base containing circular cavities connected by air channels, and then sealed a layer of their new elastomer on the top, creating a series of colour “pixels”. Pumping air into the channels inflates the elastomer membranes, causing them to stretch and changing the colours that they reflect. The colours can be controlled by varying the pressure and the size of the cavities in the 3D-printed base.
Creating structural colour: The pixelated platform includes a base with air channels, a supporting layer and a pneumatically actuated membrane of chiral nematic main-chain liquid crystalline elastomer (MCLCE). (Courtesy: Nat. Mater. 10.1038/s41563-021-01075-3)
The researchers demonstrated that an increase in pressure of just 9.6 kPa was enough to switch the wavelengths reflected by the pixels from near-infrared through red, green and blue to ultraviolet. They also showed that by using multiple air channels to activate groups of pixels, or individual pixels, they could create displays such as number countdowns.
As well as displays, the researchers suggest the material could be used for colour-changing soft robots and cryptic colouration, such as disruptive imaging and countershading. Yang says that because the material changes colour when subjected to a very small deformation, it could be used to create temperature, pressure or mechanical sensors.
Yang also suggests that the material may be suitable for building smart windows that reflect more infrared light as the ambient temperature rises. “That’s one of the interests, whether we can use the heat induced expansion of the air,” she tells Physics World.
When a simple system of two liquids is driven out of equilibrium, it can generate a far more diverse array of structures than previously thought, new experiments have shown. The discovery was made by Jaakko Timonen, Nikos Kyriakopoulos and colleagues at Aalto University in Finland, who identified structures including filaments, lattices, and square-shaped droplets, when applying electric fields to thin sheets of different combinations of conductive, polarizable oils.
If two liquids are brought together, they will usually settle into the steady state of thermodynamic equilibrium. Depending on their miscibility and relative densities, they can form uniform mixtures (such as water and ethanol), separated layers (such as oil floating on top of water) – or emulsions such as mayonnaise. Far more interesting behaviour can emerge if these systems are driven out of thermodynamic equilibrium by the application of external forces such as an electric field.
Non-equilibrium behaviours underly a wide array of fascinating phenomena: from the emergence of unexpected patterns within materials, to collective motions of self-propelling microbes. As a result, they are of immense interest across different numerous fields: from physics to biology. With existing theories, however, it can be incredibly challenging to predict the nature of the complex states that emerge.
Polarized oils
To shed new light on two liquid systems, the Aalto team designed a new set of experiments involving several different oils: each with different densities and electrical conductivities; and which become electrically polarized to different degrees when electric fields are applied.
When a thin sheet of any combination of two of the oils was subjected to an electric field, charges would build up at the interface separating them. Through the effect of electrohydrodynamic shearing, these charges were set into motion, driving the entire system out of equilibrium. The result was a wholly unexpected diversity of patterns and shapes.
At low levels of shearing, the researchers identified symmetry breaking at the interface between the oils, creating 1D patterns of corrugation. When shearing was slightly stronger, topological changes at the interface gave rise to microfilaments that rolled and rotated about their axes, and which could connect to form intricate networks.
Strong shearing
Alternatively, the oils could also form 2D lattices – which are virtually unheard of in liquids. When shearing was at its strongest, the system transitioned into square, hexagonal, and doughnut-shaped droplets, which could actively propel themselves forwards.
Timonen’s team hope that their discoveries could soon enable researchers to create temporary droplets, filaments, and lattices with well-defined sizes, which could be turned on and off by an applied voltage. If achieved, this could lead to many exciting applications: including controllable optical devices, and the ability to mimic the dynamics of swimming microbes, such as bacteria and algae.
A new memory assessment technique could pave the way for earlier diagnosis of Alzheimer’s disease, the underlying cause of around 60% of dementia cases. The approach uses electroencephalography (EEG) to measure brain activity while participants watch flashing images on a computer screen.
Current diagnostic tests for Alzheimer’s disease are not effective during its early stages, meaning that Alzheimer’s is typically only diagnosed late in the disease process. As such, there’s a real need for early diagnosis tools that could enable the timely initiation of lifestyle interventions to slow the rate of cognitive decline. Such a tool could also help drug development, through earlier and more accurate identification of dementia patients in clinical trials.
The research team developing the new EEG-based test, led by cognitive neuroscientist George Stothart from the University of Bath, think that it could lower the age of diagnosis by up to five years in the near future. In the longer-term, the technique – known as Fastball EEG – has potential to improve this further.
EEG works by using multiple electrodes placed on the scalp (in an EEG cap) to record the brain’s electrical activity. Fastball uses a method called fast periodic visual stimulation (FPVS), which measures brain signals as the subject views a series of rapidly presented images, a few of which are repeated at slower intervals. The technique is highly effective at picking up small, subtle changes in brain waves that occur when a person remembers an image.
The big advantage of Fastball EEG is that it is completely passive. The person performing the test is not given any instructions prior to the task, which is important as dementia patients may struggle to follow complex instructions, and is not asked to reflect on, respond to or remember any items. The technique is also low-cost, non-invasive and uses technology that’s already available in hospitals.
“Fastball offers a genuinely novel way of measuring how our brain is functioning,” Stothart explains in a press statement. “The person being assessed doesn’t need to understand the test, or even respond, they simply watch a screen of flashing images and by the way we manipulate the images that appear we can learn an enormous amount about what their brain is, or is not, able to do.”
Fastball trials
The FPVS procedure induces two discrete frequency responses in the EEG, which reflect the participant’s periodic neural responses to the stimuli. The first reflects visual processing at the image presentation frequency. The second mirrors the brain’s response to previously seen images and reflects the patient’s recognition memory. Analysing the EEG spectrum at this second, slower frequency can quantify the patient’s memory response.
Data analysis: George Stothart examines the Fastball EEG data. (Courtesy: Nic Delves Broughton/University of Bath)
In a study reported in Brain, Stothart and collaborators tested Fastball EEG in 20 patients with Alzheimer’s disease, 20 healthy older adults and 20 healthy younger adults. Participants performed the Fastball task, which took less than 3 min, under three conditions: recognition, repetition and control. In the recognition condition, eight images were viewed beforehand, and then repeatedly shown within a stream of unique previously-unseen images. In the repetition condition, the eight images were not seen in advance but were repeated during the Fastball task. In the control condition, subjects only viewed a stream of novel images.
For both the recognition and repetition conditions, Fastball EEG detected significantly impaired recognition memory in Alzheimer’s disease patients compared with healthy older control subjects. There were no differences between the two groups under the control condition, where image recognition was not included. The Fastball test could also discriminate Alzheimer’s disease patients from healthy older adult controls, with an accuracy of 86%. No significant performance differences were seen between older and younger healthy controls.
After the Fastball task, participants completed a forced-choice task, in which they had to identify a previously seen image from two alternatives. Here, the researchers observed little difference between Alzheimer’s disease patients and controls, suggesting that Fastball was more sensitive to memory performance than this behavioural recognition test.
The researchers conclude that this new method for measuring visual recognition memory is sensitive to changes in recognition memory processes in Alzheimer’s disease that would be missed by behavioural testing alone. “The tests we currently use to diagnose Alzheimer’s miss the first 20 years of the disease, which means we are missing huge opportunities to help people,” says Stothart. “Ultimately, the Holy Grail of a tool like this would be a dementia screening tool used in middle age for everyone, regardless of symptoms, in the same way we test for high blood pressure. We are a long way from that, but this is a step towards that goal.”
The team has now extended the approach into earlier stages of dementia, examining subjects with mild cognitive impairment, which for some people (although not all) is a precursor to Alzheimer’s disease. “We are conducting a longitudinal study of patients with mild cognitive impairment using an expanded battery of Fastball tasks designed to capture a range of cognitive functions,” Stothart tells Physics World.
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Answers will be published in the October issue of Physics World. Please note that this crossword is just for fun; there are no prizes.
Chinese photographer Shuchang Dong has beaten thousands of amateur and professional photographers from around the world to win the 2021 Astronomy Photographer of the Year. The award – now in its 13th year – is run by the UK’s Royal Observatory Greenwich in association with insurer Liberty Specialty Markets and BBC Sky at Night Magazine. Dong’s image – The Golden Ring – depicts the annular solar eclipse that occurred on 21 June 2020 and was taken in Ali in Tibet using a Fujifilm XT-4 camera.
As well as winning the £10,000 top prize, Dong’s image will be on display along with other selected pictures at an exhibition at the observatory that opened on 18 September. The competition received over 4500 entries from 75 countries. You can find the other entries here.
From photography to dance, the artist Geraldine Cox has teamed-up with physicists at the UK’s Imperial College and professional dancers to create Elemental Dances, which is a series of six educational videos that explore the nature of atoms and molecules through dance. Aimed at children age 7–11, the videos are 20–30 min long and each one begins with a physicist giving a brief explanation of a physical phenomenon such as Brownian motion. Then the children are encouraged to explore the motion involved in the effect by dancing. Other topics covered include atomic spectra and the vibrations and rotations of a water molecule.
The videos (see trailer above) have already been used in some primary schools and teacher Paul Tyler says, “The content is very well explained and the range of scientists delivering the explanations is brilliant. Dance is such a clever way of letting children explore the different concepts and it is wonderfully delivered by the dancers.”
Earlier this year, Cox was a guest on the Physics World Weekly podcast and talked about how she draws on her background in physics to create pieces inspired by the patterns of nature.
Art sometimes involves creating an illusion, be it visual or in sound. But did you know that there are illusions that fool our sense of touch? Researchers in Switzerland have shown that our tactile perception of the frequency at which a surface is vibrating can be altered by changing the amplitude of the vibration.
Vibrational metamerism
Human subjects were asked to compare two vibrations and say which is at the higher frequency. Daniel Huber and colleagues found that their ability to do so was affected by the relative amplitudes of the two vibrations. Indeed, they found that at certain amplitudes, the subjects believed that vibrations at two different frequencies were at the same frequency – an effect called metamerism. The team performed the same experiment with mice as subjects and saw similar results.
Huber and colleagues say that their observations could be useful for creating music for people who have trouble hearing and rely on feeling vibrations. Indeed, the team now plans to work with deaf volunteers and musicians to explore that avenue. Their research is described in Nature Communications.
Five amateur astronomers from South America and Europe have captured a burst of light on Jupiter that was the result of an asteroid crashing into the planet’s atmosphere. It is thought that the flash on 13 September – known as a meteor “bolide” – may have been created by a body tens of metres across. It is only the seventh time in history that observers have recorded an impact flash on the gas giant.
José Luis Pereira from Brazil is among those to image the impact. On the evening of the 13 September he was recording videos of the planet with a 275 mm-aperture Newtonian telescope when he spotted a “glow” in one of the captures. “At the time I didn’t give it much importance because I thought it was something related to the capture parameters due to bad weather conditions,” he told Physics World.
I was extremely emotional as it’s something I’ve wanted to discover for many years
José Luis Pereira
Pereira nevertheless ran the data through software that is designed to look for impact flashes on Jupiter, which alerted him to a possible event in one of the videos. Pereira subsequently got in touch with fellow amateur astronomer Marc Delcroix, who leads the development of the DeTeCt program, who was able to confirm his finding. “I was extremely emotional as it’s something I’ve wanted to discover for many years,” says Pereira. “It doesn’t even feel like it’s real.”
Impact zone
Delcroix adds that as well as the five observers who independently discovered the impact, another four also uncovered signs of it in their data after news of the event got out. The detection of the bolide on the Solar System’s largest planet highlights the growing success of regular, international, observing campaigns by amateur astronomers. It also marks the second time that DeTeCt has been involved in identifying a fireball on Jupiter – the other being the discovery, by a US-based astronomer, of an impact flash in 2019.
Delcroix says some 140 observers currently send him their results from using DeTeCt, with the number of users growing appreciably after this latest event. “My hope is to have a more generalised usage of DeTeCt to maximise the number of impacts detected and get a more robust impact frequency estimation on Jupiter,” he says.
As well as aiming to increase the number of astronomers involved in the DeTeCt project, Delcroix hopes that observers will use the software to expand the hunt for meteor fireballs on another of the gas giants, Saturn. If that search proves fruitful, we may soon see – in addition to the seven impact events so far detected on Jupiter – the first discovery of a bolide in the Saturnian skies.
Impact studies can provide important data for researchers trying to understand the nature of the more remote parts of our planetary neighbourhood.
“[Observing impacts] tells us something about the present-day population of small bodies in the outer Solar System, and reveals the dynamic nature of these systems,” says Leigh Fletcher, a planetary scientist at the University of Leicester. “If we see larger bodies impacting, this provides an excellent opportunity to study the atmospheric response to the energy and chemistry of these impactors.”
Chronic pain, classified as persistent pain that lasts longer than three to six months, remains an area of considerable unmet medical need. A new treatment that uses electrodes to deliver alternating pulses of ultralow-frequency (ULF) current could help address this need. In a pilot trial, the treatment improved pain ratings by as much as 90% after 15 days of use. Unlike existing clinical neuromodulation techniques, this ULF approach avoids tissue damage and other side effects.
The research team, headed up at Kings College London, used experimental, theoretical and clinical approaches to investigate the potential of the new ULF neuromodulation technique. In research described in Science Translational Medicine, the team examined whether ULF current waveforms can effectively impede the conduction of sensory signals in laboratory rats and reduce chronic pain in patients.
Neuromodulation, the use of electrical currents to block the transmission of pain signals between neurons, has been employed as a non-pharmacological treatment for chronic pain for decades. Existing technologies, however, can be invasive, have limited efficacy and cause side effects.
Spinal cord stimulation, for example, utilizes an implanted device to produce pulsed electrical signals in the region of the spinal cord. The treatment has had limited clinical success, only working for some patients and alleviating pain for short periods of time. It can also cause paresthesia, a sensation of numbness, tingling or burning. Previous research has also explored the application of direct current (DC), which can effectively block the conduction of action potentials (which transmit pain signals), but leads to tissue damage and electrode degradation if maintained.
In this latest work, Stephen McMahon from the Wolfson Centre for Age-Related Diseases and collaborators developed a form of ULF biphasic current. Because the slowly cycling current waveform has a period of more than 10 s, far longer than the millisecond time constant of neuronal action potentials, it effectively mimics DC conditions, but with alternating polarity that avoids potential tissue or electrode damage. Using computational modelling, they determined that the mechanism of immediate conduction block at the plateau phases of the ULF waveform was the same as that produced by DC.
In anesthetized rats, this waveform produced a rapidly developing and completely reversible conduction block in more than 85% of spinal sensory nerve fibres excited by peripheral stimulation. Sustained ULF currents at lower amplitudes led to a slower onset but reversible block. In separate experiments, the researchers verified that ULF currents blocked sensory neuron ectopic activity, an important driver of neuropathic pain, in rats with spinal nerve injury.
Clinical evaluation
The team tested the efficacy of epidural ULF therapy in 20 patients with chronic lower back pain. Eighteen patients received the full treatment during five clinical visits over 15 days, with two withdrawing early due to surgical site infections. The therapy was well tolerated, with none of the patients experiencing muscle weakness or paresthesia.
The researchers assessed pain using the visual analogue scale (VAS), in which patients report their pain level as a distance along a 100 mm line, ranging from no pain at 0 mm to severe pain at the far end. Epidural ULF significantly reduced the patients’ pain ratings, from a mean score of 74.6±1.6 mm at screening, to 15.7±4.1 mm at day seven, and 7.6±3.1 mm at day 15. These changes represent 79% and 90% reduction in pain ratings, respectively. One week after the treatment finished, pain had begun to increase again, ultimately reverting to original values.
Study participants reported that pain started to reduce within 2 to 12 hr of the initial treatment, and increased again within one day of ULF cessation. During the treatment time, the subjects found it easier to take walks and perform other types of physical activity. Seven of the 19 patients who received at least seven days of treatment achieved 100% back pain relief, with an additional 10 achieving at least an 80% improvement, and another achieving 50% pain relief.
Eleven participants also suffered from leg pain, with a VAS score of 69.5±5.6 mm at screening. This score reduced to 5.1±2.0 mm on the final day of treatment. Six patients achieved 100% pain relief, an additional four achieved 80% or greater, and one achieved 50% pain relief.
The researchers conclude that ULF could provide an effective alternative treatment for chronic pain, noting that their results warrant longer studies to define the technique’s long-term safety and further interrogate its mechanisms of action.
In this episode of the Physics World Weekly podcast the historian Alex Wellerstein explains how the US has kept its nuclear secrets since the Second World War. The author of Restricted Data: the History of Nuclear Secrecy in the United States, he explains how the country has walked the fine line between trying to prevent rogue actors from developing weapons and encouraging the peaceful use of nuclear technologies.
Also in this week’s podcast is Kim Eggleton, who is research integrity and inclusion manager at IOP Publishing. She explains why the scholarly publisher is offering double anonymous peer review on its journals – whereby the identity of the authors is hidden from the reviewers and vice versa.
Alex Wellerstein was interviewed by Physics World’s Margaret Harris, who has reviewed Restricted Data in the September 2021 issue of the magazine.
