physicsworld--2020-10-08--New auxetic material stretches the limits - Physics World

Take a rubber band , stretch it along its length , and it will shrink in the other two directions , getting narrower and thinner as you pull .
The amount of “ perpendicular contraction ” that occurs is determined by the material ’ s Poisson ratio , which in such cases is a positive number .
Some materials , however , do the exact opposite when stretched .
Known as “ auxetics ” , they expand in one of the perpendicular directions and therefore have a negative Poisson ratio .
The first artificial auxetic materials were made about 40 @ @ @ @ @ @ @ nature .
Some are complex biomaterials , such as human tendons and cat , cow and salamander skin .
There are also inorganic auxetics , including palladium , copper , gold and other face-centred cubic metals , as well as certain zeolites such as natrolite ( Na Al Si O ) .
When stretched , these materials undergo a clever internal reorganization , forming voids that lower the overall density .
Synthetic auxetics take the lead from nature ’ s elegance , being carefully engineered so that they have a similarly porous internal @ @ @ @ @ @ @ when stretched makes auxetics fascinating from a scientific and theoretical point of view .
But they also have some cool everyday applications .
The sole on Nike ’ s Flyknit running shoe , for example , has a macroscopic auxetic geometric structure .
It expands when a runner hits their foot on the ground , reducing uncomfortable pressure points in the process .
Despite such successes , it ’ s fair to say that applications of auxetics in other areas have been more limited .
Part of the problem is that many artificial @ @ @ @ @ @ @ structure , with the individual pores usually being bigger than a micron in size .
An auxetic material can therefore expand only by a certain amount : any more and it will weaken and possibly collapse .
But in 2018 Devesh Mistry – who was then one of my PhD students at the University of Leeds , UK – made a ground-breaking and entirely unexpected discovery .
At the time , Mistry was studying the mechanical properties of liquid-crystal elastomers – a rubber-like material based on the standard liquid crystals found in flat-screen @ @ @ @ @ @ @ are curious in that they flow ( like a liquid ) yet still retain some order ( like a crystal ) .
Subtle differences in the amount of order in these fluids create many different phases of liquid crystal , the simplest being the “ nematic ” phase .
Nematic liquid crystals usually have elongated , rod-like molecules , which all line up so that their long axes point roughly in the same direction , like knives in a cutlery drawer .
How well the molecules are aligned with that overall direction ( @ @ @ @ @ @ @ is quantified by the “ order parameter ” S = < 3cos2θ – 1 > / 2 , where θ is the angle between the molecules and the director .
This parameter can vary from 1 ( for a perfect crystal ) to 0 ( corresponding to a randomly oriented liquid ) and even as low as –0.5 ( negative order , which we ’ ll return to later ) .
Most nematic phases have an order parameter of S ≈ 0.6 , meaning there ’ s some fluctuation in the overall alignment @ @ @ @ @ @ @ Now although most liquid crystals – including those in displays – contain small molecules , it ’ s also possible to obtain liquid-crystalline behaviour from long-chain polymers that have small , rod-like units strung out along their backbone ( figure 1a ) or stuck out from the side ( figure 1b ) .
When these rods line up , the polymers act like liquid crystals .
What ’ s more , if the rods on one polymer chain are physically connected ( or “ cross-linked ” ) to more than one chain , @ @ @ @ @ @ @ liquid-crystal elastomer ( LCE ) that Mistry was studying .
Combining the elasticity of an ordinary elastomer ( like rubber ) with the self-organization of a liquid crystal , these soft materials have some unusual anisotropic mechanical properties .
But because there was no chemist on our Leeds team at the time for him to draw on , Mistry decided to develop an LCE that he could easily synthesize himself using a known synthetic pathway and commercially available monomers – a “ physicist-friendly ” LCE as he put it .
Using techniques borrowed @ @ @ @ @ @ @ was able to make highly uniform thin films of his materials , in which the orientation of the rods can be controlled over large areas .
Having developed his new LCE material , which had rods as side groups , Mistry and a group of technicians from Leeds started building a special piece of equipment for testing its mechanical properties .
The equipment was designed so that it could fit onto the stage of a polarizing microscope – one of the tools-of-the-trade in liquid-crystal physics .
Using the rig , Mistry was able @ @ @ @ @ @ @ at a chosen point in the LCE , which indicates the amount of local liquid-crystalline order , and monitor how this changes as the strain is increased .
When he pulled the film in the x direction – perpendicular to the director , which pointed in the y direction ( figure 1c ) – nothing of note initially happened .
The material simply stretched in a soft elastic fashion and the director remained about 90° to the stretching direction .
However , once it was stretched beyond a threshold strain of 0.9 , @ @ @ @ @ @ @ with the strain axis – in other words , the angle between the director and the stretching direction fell to 0° .
By simultaneously measuring the dimensions of the LCE film , Mistry concluded that it was behaving as an auxetic material – it was getting thicker in the z direction , at 90° to the direction in which it was being stretched .
There were two possible explanations for this unexpected auxetic behaviour .
The first , rather mundane , option was that the strain on the sample had simply lowered the @ @ @ @ @ @ @ pores had formed in it as with all other ordinary auxetics .
But when Mistry carried out further mechanical studies using cryo-scanning electron microscopy and atomic-force microscopy , it appeared that the volume – and hence density – remained unchanged , which meant that no nanometre-sized pores had formed .
That therefore left the other , more exciting , option , which was that the LCE ’ s auxetic behaviour was occurring at the molecular scale .
Incredibly , Mistry had discovered a material that , when strained beyond a certain threshold value @ @ @ @ @ @ @ the direction in which it was being stretched without the formation of voids .
Somehow the polymer was rearranging itself at a local molecular level to trigger auxetic behaviour ( figure 1d ) .
What ’ s more , Mistry soon noticed that the threshold strain dictating the onset of auxetic behaviour coincided with what appeared to be an order parameter of zero – and potentially even less than zero .
An order parameter less than zero might seem odd , but in this case it means that the rod-like units are randomly @ @ @ @ @ @ @ material , while the director itself points in the z-direction , out of the plane .
Further insights have been uncovered by Thomas Raistrick , one of my current PhD students .
His quantitative Raman-scattering measurements have shown that the uniaxial order of the material ( meaning it has only one axis of anisotropy ) falls to zero as the material is stretched .
But just before the threshold strain , biaxial behaviour emerges ( meaning the material now has two axes of anisotropy ) .
As the strain increases further , the @ @ @ @ @ @ @ state .
We need to do more work , but it ’ s clear that a complex interchange of order and symmetry causes the auxetic response , with further insights hopefully emerging soon .
What ’ s so interesting about this LCE ’ s auxetic behaviour is that it occurs at the molecular scale rather than relying on the behaviour of macroscopic pores found in other “ first-generation ” synthetic auxetic materials .
It therefore does not become inherently weaker when stretched , which means it could be used , say , as @ @ @ @ @ @ @ material that is likely to come under a lot of impact .
The material would then act as a shock absorber – thickening in response to the force , rather than becoming thinner like a standard positive-Poisson-ratio material .
These transparent molecular auxetics could also be useful in the automotive industry to protect car windows , which usually have several layers of glass separated by layers of polymer .
When hit , the induced strain makes all the layers shrink and so can become unstuck or “ delaminate ” .
But if you @ @ @ @ @ @ @ Poisson ratio , it would – if hit – expand against each layer of glass and stop any delamination from occurring .
Molecular auxetics could also , for the same reason , be used in solar cells , which usually come with a 25-year warranty and need to stay robust for long periods .
Our team at Leeds , including Mariam Hussain , Richard Mandle , Ethan Jull , Keith Rollins and Peter Hine , is currently exploring these protection and delamination prevention applications .
We believe that molecular auxetic LCEs could be @ @ @ @ @ @ @ re robust , transparent and thicken when stretched , but also because we can effectively tune these materials at the molecular level simply by adjusting their chemical make-up .
• The author thanks Ethan Jull of the University of Leeds for the original draft of this article

Physics World, where it appeared under the headline "Stretching the limits". Members of the Institute of Physics can enjoy the full issue Taken from the October 2020 issue of, where it appeared under the headline "Stretching the limits". Members of the Institute of Physics can enjoy the full issue via the Physics World app
Most materials get thinner when stretched, but “auxetics” do the opposite and get thicker. Helen Gleeson describes her group’s discovery of a material that is auxetic at the molecular level, which could be used in everything from body armour to laminated glass
Material magic Helen Gleeson with her former PhD student Devesh Mistry, who discovered auxetic behaviour in a liquid-crystal elastomer. Mistry used a specially designed set-up that could fit on the stage of a polarizing microscope (pictured) to test the mechanical properties of the material. (Courtesy: University of Leeds)
Take a rubber band, stretch it along its length, and it will shrink in the other two directions, getting narrower and thinner as you pull. The amount of “perpendicular contraction” that occurs is determined by the material’s Poisson ratio, which in such cases is a positive number. Some materials, however, do the exact opposite when stretched. Known as “auxetics”, they expand in one of the perpendicular directions and therefore have a negative Poisson ratio.
The first artificial auxetic materials were made about 40 years ago but they also exist in nature. Some are complex biomaterials, such as human tendons and cat, cow and salamander skin. There are also inorganic auxetics, including palladium, copper, gold and other face-centred cubic metals, as well as certain zeolites such as natrolite (Na 2 Al 2 Si 3 O 10 ). When stretched, these materials undergo a clever internal reorganization, forming voids that lower the overall density.
Synthetic auxetics take the lead from nature’s elegance, being carefully engineered so that they have a similarly porous internal geometry. Their ability to get thicker when stretched makes auxetics fascinating from a scientific and theoretical point of view. But they also have some cool everyday applications. The sole on Nike’s Flyknit running shoe, for example, has a macroscopic auxetic geometric structure. It expands when a runner hits their foot on the ground, reducing uncomfortable pressure points in the process.
Pain relief Auxetic structures are already used in Nike’s Flyknit running shoe. The unusual auxetics discovered by the University of Leeds team could lead to new applications entirely. (Courtesy: Nike)
Despite such successes, it’s fair to say that applications of auxetics in other areas have been more limited. Part of the problem is that many artificial auxetic materials have a porous, foamy structure, with the individual pores usually being bigger than a micron in size. An auxetic material can therefore expand only by a certain amount: any more and it will weaken and possibly collapse. But in 2018 Devesh Mistry – who was then one of my PhD students at the University of Leeds, UK – made a ground-breaking and entirely unexpected discovery.
Serendipitous success
At the time, Mistry was studying the mechanical properties of liquid-crystal elastomers – a rubber-like material based on the standard liquid crystals found in flat-screen TVs and mobile-phone displays. Liquid crystals are curious in that they flow (like a liquid) yet still retain some order (like a crystal). Subtle differences in the amount of order in these fluids create many different phases of liquid crystal, the simplest being the “nematic” phase.
Nematic liquid crystals usually have elongated, rod-like molecules, which all line up so that their long axes point roughly in the same direction, like knives in a cutlery drawer. How well the molecules are aligned with that overall direction (known as the “director”) is quantified by the “order parameter” S = <3cos2θ – 1> / 2, where θ is the angle between the molecules and the director. This parameter can vary from 1 (for a perfect crystal) to 0 (corresponding to a randomly oriented liquid) and even as low as –0.5 (negative order, which we’ll return to later). Most nematic phases have an order parameter of S ≈ 0.6, meaning there’s some fluctuation in the overall alignment of the molecules around the director.
1 Auxetic behaviour in liquid-crystal elastomers Liquid crystals found in mobile-phone screens or TVs usually consist of rod-like molecules that point in roughly the same direction, known as the “director”. However, liquid-crystal behaviour can also be obtained from long-chain polymers that have rod-like units strung along the backbone (a) or stuck out from the side (b). If the neighbouring chains are physically connected, you end up with a “liquid-crystal elastomer”, which has some unusual mechanical properties, as our group at the University of Leeds, UK, found when we strained a thin film of the material in the x direction (c). We discovered that its strain in the z direction (red dots in (d)) and associated change in thickness falls as expected before suddenly increasing again. At this threshold strain of 0.9, the angle (purple squares in (d)) between the director and the x-axis drops from 90° (i.e. perpendicular to the strain) to 0° (i.e. parallel to the strain).
Now although most liquid crystals – including those in displays – contain small molecules, it’s also possible to obtain liquid-crystalline behaviour from long-chain polymers that have small, rod-like units strung out along their backbone (figure 1a) or stuck out from the side (figure 1b). When these rods line up, the polymers act like liquid crystals. What’s more, if the rods on one polymer chain are physically connected (or “cross-linked”) to more than one chain, you end up with the kind of liquid-crystal elastomer (LCE) that Mistry was studying.
Combining the elasticity of an ordinary elastomer (like rubber) with the self-organization of a liquid crystal, these soft materials have some unusual anisotropic mechanical properties. But because there was no chemist on our Leeds team at the time for him to draw on, Mistry decided to develop an LCE that he could easily synthesize himself using a known synthetic pathway and commercially available monomers – a “physicist-friendly” LCE as he put it. Using techniques borrowed from the liquid-crystal display industry, Mistry was able to make highly uniform thin films of his materials, in which the orientation of the rods can be controlled over large areas.
Strange behaviour
Having developed his new LCE material, which had rods as side groups, Mistry and a group of technicians from Leeds started building a special piece of equipment for testing its mechanical properties. The equipment was designed so that it could fit onto the stage of a polarizing microscope – one of the tools-of-the-trade in liquid-crystal physics. Using the rig, Mistry was able to measure the angle of the director at a chosen point in the LCE, which indicates the amount of local liquid-crystalline order, and monitor how this changes as the strain is increased.
When he pulled the film in the x direction – perpendicular to the director, which pointed in the y direction (figure 1c) – nothing of note initially happened. The material simply stretched in a soft elastic fashion and the director remained about 90° to the stretching direction. However, once it was stretched beyond a threshold strain of 0.9, the director rapidly began to line up with the strain axis – in other words, the angle between the director and the stretching direction fell to 0°. By simultaneously measuring the dimensions of the LCE film, Mistry concluded that it was behaving as an auxetic material – it was getting thicker in the z direction, at 90° to the direction in which it was being stretched.
There were two possible explanations for this unexpected auxetic behaviour. The first, rather mundane, option was that the strain on the sample had simply lowered the material’s density, meaning that pores had formed in it as with all other ordinary auxetics. But when Mistry carried out further mechanical studies using cryo-scanning electron microscopy and atomic-force microscopy, it appeared that the volume – and hence density – remained unchanged, which meant that no nanometre-sized pores had formed.
That therefore left the other, more exciting, option, which was that the LCE’s auxetic behaviour was occurring at the molecular scale. Incredibly, Mistry had discovered a material that, when strained beyond a certain threshold value (0.9), thickened perpendicular to the direction in which it was being stretched without the formation of voids. Somehow the polymer was rearranging itself at a local molecular level to trigger auxetic behaviour (figure 1d).
What’s more, Mistry soon noticed that the threshold strain dictating the onset of auxetic behaviour coincided with what appeared to be an order parameter of zero – and potentially even less than zero. An order parameter less than zero might seem odd, but in this case it means that the rod-like units are randomly oriented in the x–y plane of the material, while the director itself points in the z-direction, out of the plane.
Further insights have been uncovered by Thomas Raistrick, one of my current PhD students. His quantitative Raman-scattering measurements have shown that the uniaxial order of the material (meaning it has only one axis of anisotropy) falls to zero as the material is stretched. But just before the threshold strain, biaxial behaviour emerges (meaning the material now has two axes of anisotropy). As the strain increases further, the material begins to return to a uniaxial state. We need to do more work, but it’s clear that a complex interchange of order and symmetry causes the auxetic response, with further insights hopefully emerging soon.
Applications ahead
What’s so interesting about this LCE’s auxetic behaviour is that it occurs at the molecular scale rather than relying on the behaviour of macroscopic pores found in other “first-generation” synthetic auxetic materials. It therefore does not become inherently weaker when stretched, which means it could be used, say, as body armour, where you need a material that is likely to come under a lot of impact. The material would then act as a shock absorber – thickening in response to the force, rather than becoming thinner like a standard positive-Poisson-ratio material.
Clear benefits This transparent liquid-crystal elastomer displays auxetic behaviour when stretched – not because voids form inside it (as with ordinary auxetics) but because the structure reorganizes internally at a molecular level. (Courtesy: Ethan Jull, University of Leeds)
These transparent molecular auxetics could also be useful in the automotive industry to protect car windows, which usually have several layers of glass separated by layers of polymer. When hit, the induced strain makes all the layers shrink and so can become unstuck or “delaminate”. But if you had an auxetic material with a negative Poisson ratio, it would – if hit – expand against each layer of glass and stop any delamination from occurring. Molecular auxetics could also, for the same reason, be used in solar cells, which usually come with a 25-year warranty and need to stay robust for long periods.
Our team at Leeds, including Mariam Hussain, Richard Mandle, Ethan Jull, Keith Rollins and Peter Hine, is currently exploring these protection and delamination prevention applications. We believe that molecular auxetic LCEs could be game-changers – not just because they’re robust, transparent and thicken when stretched, but also because we can effectively tune these materials at the molecular level simply by adjusting their chemical make-up.
The author thanks Ethan Jull of the University of Leeds for the original draft of this article


physicsworld--2020-10-08--Black hole’s shadow boosts Einstein’s general theory of relativity - Physics World

Einstein ’ s general theory of relativity has triumphed once again after being tested in the strongest gravitational field to date .
Dimitrios Psaltis at the University of Arizona and members of the Event Horizon Telescope ( EHT ) collaboration did their analysis using recent images of M87* , which is a supermassive black hole at the centre of a nearby galaxy .
Their results set the stage for even more stringent tests of general relativity in the near future .
For over a century , general relativity has had an excellent track record in explaining observations of the universe @ @ @ @ @ @ @ leaves some big questions unanswered : including how to unify gravity with quantum mechanics and the surprise discovery in 1998 of the universe ’ s accelerating expansion .
As a result , physicists are looking for subtle flaws in general relativity that could lead to the development of a more complete theory .
One way to study the theory ’ s limitations is to search for discrepancies in how it describes distortions of spacetime by the gravitational fields of massive objects .
Initially , these tests used objects in the solar system – @ @ @ @ @ @ @ recently , gravitational waves created by merging black holes and observed by the LIGO–Virgo collaboration have enabled tests in the gravitational fields of objects as heavy as 150 solar masses .
Yet despite the increasingly rigorous constraints imposed by these results , cracks have yet to show in Einstein ’ s theory .
M87* has a mass of about 3.5–6.6 billion Suns and its gravitational field is the largest ever used to test general relativity .
In 2019 , the EHT released its celebrated image of the shadow of M87* – a dark @ @ @ @ @ @ @ hot plasma .
General relativity provides a precise prediction of the size of the shadow and in the case of M87* , the observed size is within 17 % of general relativity ’ s prediction .
It is possible , therefore that a modified version of general relativity could do a better job at predicting the size of the M87* shadow .
To test this , Psaltis and colleagues considered alternative models of gravity that modify the general theory of relativity .
They focussed on parameters of these alternative models that affected the @ @ @ @ @ @ @ the shadow .
By comparing these predictions to the observed shadow , they we able to constrain modifications to Einstein ’ s theory by a factor of almost 500 compared with earlier solar system tests .
The new constraints are similar to those derived from gravitational wave observations .
The EHT collaboration now hopes to impose even stricter limits by imaging the shadow of Sagittarius A* – the supermassive black hole at the centre of our own galaxy , whose mass is far more precisely defined than M87* .
The research is described @ @ @ @ @

Supermassive test: this simulation of the region around M87 shows the motion of plasma as it swirls around the black hole. The bright thin ring that can be seen in blue is the edge of the shadow. (Courtesy: L Medeiros/C Chan/D. Psaltis/F Özel/University of Arizona/Institute for Advanced Study)
Einstein’s general theory of relativity has triumphed once again after being tested in the strongest gravitational field to date. Dimitrios Psaltis at the University of Arizona and members of the Event Horizon Telescope (EHT) collaboration did their analysis using recent images of M87*, which is a supermassive black hole at the centre of a nearby galaxy. Their results set the stage for even more stringent tests of general relativity in the near future.
For over a century, general relativity has had an excellent track record in explaining observations of the universe. All the same, the theory leaves some big questions unanswered: including how to unify gravity with quantum mechanics and the surprise discovery in 1998 of the universe’s accelerating expansion. As a result, physicists are looking for subtle flaws in general relativity that could lead to the development of a more complete theory.
One way to study the theory’s limitations is to search for discrepancies in how it describes distortions of spacetime by the gravitational fields of massive objects. Initially, these tests used objects in the solar system – famously the motion of Mercury. More recently, gravitational waves created by merging black holes and observed by the LIGO–Virgo collaboration have enabled tests in the gravitational fields of objects as heavy as 150 solar masses. Yet despite the increasingly rigorous constraints imposed by these results, cracks have yet to show in Einstein’s theory.
Billions of Suns
M87* has a mass of about 3.5–6.6 billion Suns and its gravitational field is the largest ever used to test general relativity. In 2019, the EHT released its celebrated image of the shadow of M87* – a dark silhouette, surrounded by bright emission from hot plasma. General relativity provides a precise prediction of the size of the shadow and in the case of M87*, the observed size is within 17% of general relativity’s prediction.
It is possible, therefore that a modified version of general relativity could do a better job at predicting the size of the M87* shadow. To test this, Psaltis and colleagues considered alternative models of gravity that modify the general theory of relativity. They focussed on parameters of these alternative models that affected the models’ predictions of the size of the shadow.
By comparing these predictions to the observed shadow, they we able to constrain modifications to Einstein’s theory by a factor of almost 500 compared with earlier solar system tests. The new constraints are similar to those derived from gravitational wave observations. The EHT collaboration now hopes to impose even stricter limits by imaging the shadow of Sagittarius A* – the supermassive black hole at the centre of our own galaxy, whose mass is far more precisely defined than M87*.
The research is described in Physical Review Letters.


physicsworld--2020-10-08--Black holes: celebrating the 2020 Nobel Prize for Physics - Physics World

In this episode we look at the ground-breaking research on black holes that led to Roger Penrose , Reinhard Genzel @ @ @ @ @ 2020 Nobel Prize for Physics .
On hand are experts Laura Nuttall of the University @ @ @ @ @ collaboration , who studies gravitational waves from merging black holes and Harvard University ’ s @ @ @ @ @ supermassive black holes using the Event Horizon Telescope .

In this episode we look at the ground-breaking research on black holes that led to Roger Penrose, Reinhard Genzel and Andrea Ghez winning the 2020 Nobel Prize for Physics. On hand are experts Laura Nuttall of the University of Portsmouth and the LIGO–Virgo–KAGRA collaboration, who studies gravitational waves from merging black holes and Harvard University’s Shep Doeleman, who studies supermassive black holes using the Event Horizon Telescope.
Want to read more? Registration is free, quick and easy E-mail Address


physicsworld--2020-10-08--Triplet control prevents ‘lasing death’ in perovskite lasers - Physics World

On paper , perovskites make great building blocks for lasers .
In their quasi-two-dimensional form , these organic–inorganic materials exhibit tunable colour and excellent stability .
The fact that they can fabricated from low-cost starting components in simple solution-based processes makes them attractive for manufacturers , too .
There ’ s just one tiny flaw : perovskite-based lasers abruptly stop working after only a few minutes of constant operation at room temperature .
Now , however , a team of researchers in China and Japan say they have overcome this so-called “ lasing death ” by suppressing long-lived energetic states @ @ @ @ @ @ @ and quasi-2D perovskites are promising alternatives to silicon in optoelectronics devices .
While 2D perovskites are made up of stacked sheets of alternating organic and inorganic layers , their quasi-2D variants contain small regions in which organic and inorganic materials alternate in all directions ( as is the case in their 3D counterparts ) .
The quasi-2D versions also contain two different types of organic materials .
In organic semiconductors such as those that make up quasi-2D perovskites , charge carriers – electrons and holes – come together to form an energetic state @ @ @ @ @ @ @ exist in a so-called singlet state ( which has no net spin because the contributing electron spins point in opposite directions ) or in a triplet state ( in which the spins point in the same direction ) .
In both cases , the energy in the exciton can then be released as light via a process known as radiative recombination .
Triplets generally have a lower energy than singlets , however , and emit hardly any light .
Recently , researchers led by Chuanjiang Qin of the Chinese Academy of Sciences and @ @ @ @ @ @ @ found evidence that triplet excitons have lifetimes of nearly a microsecond in these materials .
These long lifetimes led them to focus on these excitons as a possible cause of lasing death .
As well as emitting very little or no light , triplet states also tend to interact with light-emitting singlets in a way that causes both to lose their energy without producing light , Qin explains .
Eliminating any triplets in perovskites would therefore prevent interference with lasing .
In their latest work , the researchers studied FAPbBr -based ( where @ @ @ @ @ @ @ two different organic cations , phenylethylammonium bromide ( PEABr ) and 1-naphthylmethylamine bromide ( NMABr ) .
The PEABr-based perovskite contains an organic cation with high triplet energy , and the NMABr-based perovskite has an organic cation with low triplet energy .
To eliminate triplets in these quasi-2D perovskites , the researchers incorporated an organic layer into the materials , which confines the triplets to a low-energy state .
Since the excitons want to move to lower energies , the long-lived triplet excitons transfer from the active ( that is , light-emitting ) @ @ @ @ @ @ @ layer , they explain .
This reduces light losses and allows for lasing under constant optical excitation ( also known as optically pumped continuous-wave , or CW lasing ) without interruption .
Qin , Adachi and colleagues also discovered that they could make their material lase continuously simply by placing it in air .
This is because oxygen can destroy triplets – a result that further suggests that light losses caused by triplets may indeed be the culprits in lasing death .
The researchers quantified their material ’ s performance by measuring the @ @ @ @ @ @ @ of the two films as they were optically powered .
They found that the ASE , or lasing , remained virtually unchanged after an hour at room temperature in air with a relative humidity of 55 % .
The lasing spectrum also maintained its narrowness ( full width at half maximum ) without shifting .
The team stress that these measurements were taken without the films being encapsulated in glass , and without a protective layer over their tops , as was the case in previous ASE stability measurements of 3D perovskites such @ @ @ @ @ @ @ , the excellent stability of their material comes from the protection provided by the larger cations on its surface .
“ We have demonstrated the key role of triplets in the lasing process of these types of perovskites and the importance of managing triplets to achieve continuous lasing , ” Adachi states in a Kyushu University press release .
“ These new findings will pave the way for the future development of a new class of electrically operated lasers based on perovskites that are low cost and easily fabricated.
” The work is @ @ @ @

A layer of perovskite is shown lasing green under continuous operation at room temperature. Credit: Chuanjiang Qin, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences
On paper, perovskites make great building blocks for lasers. In their quasi-two-dimensional form, these organic–inorganic materials exhibit tunable colour and excellent stability. The fact that they can fabricated from low-cost starting components in simple solution-based processes makes them attractive for manufacturers, too. There’s just one tiny flaw: perovskite-based lasers abruptly stop working after only a few minutes of constant operation at room temperature. Now, however, a team of researchers in China and Japan say they have overcome this so-called “lasing death” by suppressing long-lived energetic states known as triplet excitons.
Both 2D and quasi-2D perovskites are promising alternatives to silicon in optoelectronics devices. While 2D perovskites are made up of stacked sheets of alternating organic and inorganic layers, their quasi-2D variants contain small regions in which organic and inorganic materials alternate in all directions (as is the case in their 3D counterparts). The quasi-2D versions also contain two different types of organic materials.
In organic semiconductors such as those that make up quasi-2D perovskites, charge carriers – electrons and holes – come together to form an energetic state called an exciton. This entity may exist in a so-called singlet state (which has no net spin because the contributing electron spins point in opposite directions) or in a triplet state (in which the spins point in the same direction). In both cases, the energy in the exciton can then be released as light via a process known as radiative recombination. Triplets generally have a lower energy than singlets, however, and emit hardly any light.
Long triplet lifetimes
Recently, researchers led by Chuanjiang Qin of the Chinese Academy of Sciences and Chihaya Adachi at Kyushu University in Japan found evidence that triplet excitons have lifetimes of nearly a microsecond in these materials. These long lifetimes led them to focus on these excitons as a possible cause of lasing death.
As well as emitting very little or no light, triplet states also tend to interact with light-emitting singlets in a way that causes both to lose their energy without producing light, Qin explains. Eliminating any triplets in perovskites would therefore prevent interference with lasing.
In their latest work, the researchers studied FAPbBr 3 -based (where FA is formamidinium) quasi-2D perovskites with two different organic cations, phenylethylammonium bromide (PEABr) and 1-naphthylmethylamine bromide (NMABr). The PEABr-based perovskite contains an organic cation with high triplet energy, and the NMABr-based perovskite has an organic cation with low triplet energy.
Holding triplets in a low energy state
To eliminate triplets in these quasi-2D perovskites, the researchers incorporated an organic layer into the materials, which confines the triplets to a low-energy state. Since the excitons want to move to lower energies, the long-lived triplet excitons transfer from the active (that is, light-emitting) portion of the perovskites to the organic layer, they explain. This reduces light losses and allows for lasing under constant optical excitation (also known as optically pumped continuous-wave, or CW lasing) without interruption.
Qin, Adachi and colleagues also discovered that they could make their material lase continuously simply by placing it in air. This is because oxygen can destroy triplets – a result that further suggests that light losses caused by triplets may indeed be the culprits in lasing death.
Unchanged lasing intensity
The researchers quantified their material’s performance by measuring the amplified spontaneous emission (ASE) intensity of the two films as they were optically powered. They found that the ASE, or lasing, remained virtually unchanged after an hour at room temperature in air with a relative humidity of 55%. The lasing spectrum also maintained its narrowness (full width at half maximum) without shifting. The team stress that these measurements were taken without the films being encapsulated in glass, and without a protective layer over their tops, as was the case in previous ASE stability measurements of 3D perovskites such as MAPbBr 3 .
According to the researchers, the excellent stability of their material comes from the protection provided by the larger cations on its surface. “We have demonstrated the key role of triplets in the lasing process of these types of perovskites and the importance of managing triplets to achieve continuous lasing,” Adachi states in a Kyushu University press release. “These new findings will pave the way for the future development of a new class of electrically operated lasers based on perovskites that are low cost and easily fabricated.”
The work is detailed in Nature.


physicsworld--2020-10-09--Virtual imaging trials aim to optimize COVID-19 screening - Physics World

Medical imaging devices and methods are constantly evolving to meet rapidly changing clinical needs .
CT and chest radiography , for example , could provide a means to detect lung abnormalities related to COVID-19 , but the imaging parameters required to differentiate COVID-19 still need optimization .
Clinical imaging trials , however , are often expensive , time consuming and can lack ground truth .
Virtual , or in silico , imaging trials offer an effective alternative by simulating patients and imaging systems .
A group of researchers from Duke University took the first steps towards applying this approach to @ @ @ @ @ @ @ computational models of patients with COVID-19 .
In addition , they showed how these virtual models can be adapted and used together with imaging simulators for COVID-19 imaging studies .
Their proof-of-principle result , published in the American Journal of Roentgenology , paves the way towards effective and inexpensive ways of assessing and optimizing imaging protocols for rapid COVID-19 diagnosis .
Virtual imaging trials require accurate models of target subjects , also known as phantoms .
For this study , the group modelled three distinctive features of the anatomy of a COVID-19 patient @ @ @ @ @ @ @ of the abnormality ; and the texture and material of the abnormality .
For the first part , the researchers used the 4D extended cardiac-torso ( XCAT ) model developed at Duke University .
These phantoms are constructed from patient data and include thousands of body structures , as well as anatomically informed mathematical models of texture and tissue-material properties .
To model the specific abnormalities found in SARS-COV-2 patients , the group manually delineated the unique morphological features characteristic of COVID-19 in CT imaging data from 20 patients with confirmed infections .
@ @ @ @ @ @ @ as ground-glass opacities , into the XCAT models .
To make their phantom as realistic as possible , the researchers also modified the texture of each segmented abnormality to that of a material filled with fluid to match the observed pathologies .
The group produced three COVID-19 computational models with abnormalities of different shapes and locations within the lungs .
The researchers then used these models together with a validated radiographic simulator ( DukeSim ) to obtain clinically realistic virtual CT and chest-radiography images .
“ Subjectively , ” the authors explain , @ @ @ @ @ @ @ terms of shape and texture.
” “ We have developed strategies to adapt and use virtual imaging trials for imaging studies of COVID-19 , ” first author Ehsan Abadi concludes .
“ This will provide the foundation for the effective assessment and optimization of CT and radiography acquisitions and analysis tools to manage the COVID-19 pandemic.
” Future work will focus on modelling different stages and manifestations of the disease , with the aim of optimizing screening and follow-up of patients .

Simulated CT images of a COVID-19 XCAT phantom at three different radiation dose levels, representing (top left) 50, (top right) 25 and (lower left) 5 mAs settings. The lower right image shows a chest radiographic image of the same model. (Courtesy: American Roentgen Ray Society, American Journal of Roentgenology)
Medical imaging devices and methods are constantly evolving to meet rapidly changing clinical needs. CT and chest radiography, for example, could provide a means to detect lung abnormalities related to COVID-19, but the imaging parameters required to differentiate COVID-19 still need optimization. Clinical imaging trials, however, are often expensive, time consuming and can lack ground truth. Virtual, or in silico, imaging trials offer an effective alternative by simulating patients and imaging systems.
A group of researchers from Duke University took the first steps towards applying this approach to the current pandemic by developing the first computational models of patients with COVID-19. In addition, they showed how these virtual models can be adapted and used together with imaging simulators for COVID-19 imaging studies. Their proof-of-principle result, published in the American Journal of Roentgenology, paves the way towards effective and inexpensive ways of assessing and optimizing imaging protocols for rapid COVID-19 diagnosis.
Virtual COVID-19 patients…
Virtual imaging trials require accurate models of target subjects, also known as phantoms. For this study, the group modelled three distinctive features of the anatomy of a COVID-19 patient: the body; the morphological features of the abnormality; and the texture and material of the abnormality. For the first part, the researchers used the 4D extended cardiac-torso (XCAT) model developed at Duke University. These phantoms are constructed from patient data and include thousands of body structures, as well as anatomically informed mathematical models of texture and tissue-material properties.
To model the specific abnormalities found in SARS-COV-2 patients, the group manually delineated the unique morphological features characteristic of COVID-19 in CT imaging data from 20 patients with confirmed infections. They then incorporated these features, known as ground-glass opacities, into the XCAT models. To make their phantom as realistic as possible, the researchers also modified the texture of each segmented abnormality to that of a material filled with fluid to match the observed pathologies.
… virtually imaged
The group produced three COVID-19 computational models with abnormalities of different shapes and locations within the lungs. The researchers then used these models together with a validated radiographic simulator (DukeSim) to obtain clinically realistic virtual CT and chest-radiography images. “Subjectively,” the authors explain, “the simulated abnormalities were realistic in terms of shape and texture.”
First author Ehsan Abadi (third row, centre) together with the research group (Courtesy: Ehsan Abadi, Department of Radiology, Duke University)
“We have developed strategies to adapt and use virtual imaging trials for imaging studies of COVID-19,” first author Ehsan Abadi concludes. “This will provide the foundation for the effective assessment and optimization of CT and radiography acquisitions and analysis tools to manage the COVID-19 pandemic.” Future work will focus on modelling different stages and manifestations of the disease, with the aim of optimizing screening and follow-up of patients.


physicsworld--2020-10-09--Physicists pin down deuteron mass - Physics World

Physicists in Germany say they have made the world ’ s most precise measurement of the deuteron mass by comparing it to the mass of the carbon-12 nucleus .
The new work , which was carried out by confining deuterons ( which are nuclei of deuterium , or “ heavy ” hydrogen ) and carbon-12 nuclei with strong magnetic and electric fields , provides a crucial independent cross-check with previous measurements that yielded inconsistent values .
Knowing the precise masses of simple atomic nuclei such as hydrogen , its isotopes deuterium and tritium , and the molecular hydrogen ions H @ @ @ @ @ @ @ a deuteron , bound by an electron ) is crucial for testing fundamental physics theories such as quantum electrodynamics .
The mass of the deuteron can also be used to derive the mass of the neutron , which has implications for metrology as well as for atomic , molecular and neutrino physics .
To make these precise measurements , physicists often turn to Penning traps , which use extremely strong magnetic and electric fields to trap charged particles such as single deuterons and other simple ions .
Once trapped , the particles oscillate @ @ @ @ @ @ @ that depends on their mass , with heavier particles oscillating more slowly than lighter ones .
Hence , if the oscillation frequencies of two different ions are measured in the same trap , one after the other , the ratio of their masses can be calculated to a high precision ( around one part in 8.5 x 10-12 ) .
In the new work , a team from the Max Planck Institute for Nuclear Physics , the Johannes Gutenberg University , the GSI Helmholtz Centre for Heavy Ion Research and the Helmholtz Institute @ @ @ @ @ @ @ spectrometer that is dedicated to light-ion mass measurements .
The setup of this spectrometer , which the researchers dubbed LIONTRAP , consists of a stack of Penning traps .
This stack includes a highly optimized seven-electrode precision trap and two adjacent storage traps that sit within the homogeneous magnetic field of a superconducting 3.8 Tesla magnet .
The entire set-up is also kept in a near-perfect vacuum ( better than 10-17 mbar ) at a temperature of about 4K .
The researchers placed a deuteron in the storage trap before transferring it to @ @ @ @ @ @ @ determined its oscillation frequency with high precision by measuring the tiny alternating currents ( known as image currents ) induced at the inner surfaces of the trap electrodes by the charge of the moving ion .
Finally , they compared this frequency measurement with a similar one made on a carbon-12 ion ( 12C6+ ) in the same apparatus .
Study lead author Sascha Rau explains that the team chose 12C6+ because it serves as the mass standard for atoms – meaning that its mass , by definition , is equal to 12 @ @ @ @ @ @ @ the ratio of the deuteron and 12C6+ ion oscillation frequencies gives the mass of the deuteron directly , in atomic mass units .
The precision of previous measurements made using this method was limited by deviations of the trap ’ s magnetic field from its ideal form .
The German team overcame this problem by using an adjustable superconducting electromagnetic coil that is directly wound around the trap chamber , so that the trap can operate without disturbing the magnets in the other coils too much .
This set-up allowed them to measure @ @ @ @ @ @ @ by a factor of 100 .
In this way , they determined that the mass of the deuteron is 2.013553212535 ( 17 ) atomic units , where the number in brackets indicates the statistical uncertainty of the last digits .
The mass of the hydrogen molecular ion HD+ , determined by the same method , is 3.021378241561 ( 61 ) atomic units .
The new value for the mass of the deuteron is significantly smaller than the tabulated reference value .
To validate their result , Rau and colleagues therefore also calculated the @ @ @ @ @ @ @ proton and the electron they previously measured .
The new result for the deuteron is in excellent agreement with these values , they say , which suggests that the reference value for the deuteron needs to be corrected .
The result , which is published in Nature , also agrees with a recent and precise measurement of the deuteron-to- proton mass ratio made by another group .

Assembly of the LIONTRAP Penning-trap system.
© MPIK
Physicists in Germany say they have made the world’s most precise measurement of the deuteron mass by comparing it to the mass of the carbon-12 nucleus. The new work, which was carried out by confining deuterons (which are nuclei of deuterium, or “heavy” hydrogen) and carbon-12 nuclei with strong magnetic and electric fields, provides a crucial independent cross-check with previous measurements that yielded inconsistent values.
Knowing the precise masses of simple atomic nuclei such as hydrogen, its isotopes deuterium and tritium, and the molecular hydrogen ions H 2 + and HD+ (a proton and a deuteron, bound by an electron) is crucial for testing fundamental physics theories such as quantum electrodynamics. The mass of the deuteron can also be used to derive the mass of the neutron, which has implications for metrology as well as for atomic, molecular and neutrino physics.
To make these precise measurements, physicists often turn to Penning traps, which use extremely strong magnetic and electric fields to trap charged particles such as single deuterons and other simple ions. Once trapped, the particles oscillate at a particular (cyclotron) frequency that depends on their mass, with heavier particles oscillating more slowly than lighter ones. Hence, if the oscillation frequencies of two different ions are measured in the same trap, one after the other, the ratio of their masses can be calculated to a high precision (around one part in 8.5 x 10-12).
A cryogenic Penning trap mass spectrometer
In the new work, a team from the Max Planck Institute for Nuclear Physics, the Johannes Gutenberg University, the GSI Helmholtz Centre for Heavy Ion Research and the Helmholtz Institute in Mainz used a special cryogenic mass spectrometer that is dedicated to light-ion mass measurements. The setup of this spectrometer, which the researchers dubbed LIONTRAP, consists of a stack of Penning traps. This stack includes a highly optimized seven-electrode precision trap and two adjacent storage traps that sit within the homogeneous magnetic field of a superconducting 3.8 Tesla magnet. The entire set-up is also kept in a near-perfect vacuum (better than 10-17 mbar) at a temperature of about 4K.
The researchers placed a deuteron in the storage trap before transferring it to the precision trap. There, they determined its oscillation frequency with high precision by measuring the tiny alternating currents (known as image currents) induced at the inner surfaces of the trap electrodes by the charge of the moving ion. Finally, they compared this frequency measurement with a similar one made on a carbon-12 ion (12C6+) in the same apparatus.
Adjustable superconducting electromagnetic coil
Study lead author Sascha Rau explains that the team chose 12C6+ because it serves as the mass standard for atoms – meaning that its mass, by definition, is equal to 12 atomic mass units. Hence, measuring the ratio of the deuteron and 12C6+ ion oscillation frequencies gives the mass of the deuteron directly, in atomic mass units.
The precision of previous measurements made using this method was limited by deviations of the trap’s magnetic field from its ideal form. The German team overcame this problem by using an adjustable superconducting electromagnetic coil that is directly wound around the trap chamber, so that the trap can operate without disturbing the magnets in the other coils too much. This set-up allowed them to measure the magnetic field deviations and supress them by a factor of 100. In this way, they determined that the mass of the deuteron is 2.013553212535(17) atomic units, where the number in brackets indicates the statistical uncertainty of the last digits. The mass of the hydrogen molecular ion HD+, determined by the same method, is 3.021378241561(61) atomic units.
The new value for the mass of the deuteron is significantly smaller than the tabulated reference value. To validate their result, Rau and colleagues therefore also calculated the mass of HD+ using masses of the proton and the electron they previously measured. The new result for the deuteron is in excellent agreement with these values, they say, which suggests that the reference value for the deuteron needs to be corrected. The result, which is published in Nature, also agrees with a recent and precise measurement of the deuteron-to- proton mass ratio made by another group.


physicsworld--2020-10-09--Fundamental constants set upper limit for the speed of sound - Physics World

The upper limit on the speed of sound in solids and liquids depends on just two dimensionless quantities – the fine structure constant and the proton-to-electron mass ratio .
That is the surprising conclusion of physicists in the UK and Russia , who calculate that the speed limit is twice that of the highest speed of sound measured to date .
Sound propagates as a series of compressions and rarefactions in an elastic medium , with its speed varying significantly from one material to another .
Typically , sound is slowest in gases , higher in liquids and higher still @ @ @ @ @ @ @ conditions sound travels at about 340 m/s , while in water it reaches about 1500 m/s and in iron more than 5000 m/s .
These differences are due to the way that a passing wave disturbs atoms and molecules .
Thought of as hard spheres linked to one another with springs , the particles are knocked forward by their neighbours in the direction of sound propagation and in turn go on to nudge other neighbouring particles ahead of them .
But this transmission is delayed by inertia , meaning that waves move faster @ @ @ @ @ @ @ However , stiffer links also mean less delay – each particle having to move less before it triggers the movement of its neighbour .
This is why sound travels faster through iron than it does through water , for example .
Expressed mathematically , sound ’ s longitudinal speed in a material is equal to the square root of that material ’ s elastic modulus – which quantifies its resistance to compression – divided by its density .
In the latest research , Kostya Trachenko of Queen Mary University of London and colleagues @ @ @ @ @ @ @ Russian Academy of Sciences ’ Institute for High Pressure Physics set out to recast this formula in terms of fundamental constants .
Their first step was to link a material ’ s bulk modulus with the energy that binds its atoms together , given that greater stiffness implies a higher binding energy .
They then assumed that the latter term could be equated to the Rydberg energy , which is the characteristic binding energy in condensed matter .
The resulting formula proved eye-catching , particularly when expressed in terms of the fine-structure constant @ @ @ @ @ @ @ electromagnetic interactions – and then written specifically as an upper limit on the speed of sound .
The upper limit comes about when the mass of the atoms in question is the lowest mass possible – that of the hydrogen atom .
In that case , the velocity of sound can simply be expressed in terms of the proton-to-electron mass ratio ( inverted , halved and square-rooted ) , the fine-structure constant and the speed of light in a vacuum .
Inserting the relevant numbers into their formula , the researchers worked out @ @ @ @ @ @ @ in solids and liquids ( exposed to moderate pressures ) comes in at a little over 36,000 m/s .
That is still nearly 10,000 times slower than light ’ s upper limit but about twice as high as the fastest ever recorded sound wave – which stands at around 18,000 m/s and obtained in ( very stiff ) diamond .
To establish whether their equation is broadly in line with measured velocities , the researchers compared its predictions against the experimentally obtained speed of sound in 36 different elemental solids .
To do @ @ @ @ @ @ @ show how these speeds vary with the solids ’ atomic mass and on the same graph drew the straight sloping line generated by their equation – which terminates at the high end with hydrogen .
They conclude that the experimental data points more or less follow their sloping line , even if a coefficient they dropped to simplify their equation means that not all are that close .
As an additional check on their work , Trachenko ’ s team used density functional theory to calculate the speed of sound through metallic hydrogen @ @ @ @ @ @ @ very high pressures , hydrogen becomes a molecular solid , and at pressures above about 400 GPa it is predicted then to become an atomic metal .
It is this metallic state that should hold the speed record .
Modelling hydrogen in these conditions , they found that sound should propagate at up to 35,000 m/s – faster than in any other material , but still below their upper limit .
This work follows similar research that Trachenko and fellow group member Vadim Brazhkin published earlier this year , which revealed a universal @ @ @ @ @ @ @ of the proton-to-electron mass ratio and Planck ’ s constant .
By incorporating the fine-structure constant , they ended up with an expression containing two fundamental constants whose fine tuning yields a stable proton and also allows stars to ignite and produce heavier elements , enabling , as they put it , “ the existence of solids and liquids where sound can propagate ” .
Kamran Behnia of PSL University in Paris describes the work as “ simultaneously simple and deep ” .
He says he had not expected to be able to @ @ @ @ @ @ @ in a particular material “ by hand-waving arguments ” – particularly , he adds , when the resulting formula involves only fundamental constants .
As he points out , quantum mechanics is not needed to explain the propagation of sound – even if quantum mechanics is what makes the solid state possible .
“ This is why the main message of this paper comes as a surprise , ” he says .
The research is described in Science Advances .

Upper limit: a US Navy F/A-18 travelling near the speed of sound in air. The white halo comprises water droplets that have condensed from the air because of the sudden drop in pressure behind the shock cone around the aircraft . (Courtesy: John Gay/US Navy)
The upper limit on the speed of sound in solids and liquids depends on just two dimensionless quantities – the fine structure constant and the proton-to-electron mass ratio. That is the surprising conclusion of physicists in the UK and Russia, who calculate that the speed limit is twice that of the highest speed of sound measured to date.
Sound propagates as a series of compressions and rarefactions in an elastic medium, with its speed varying significantly from one material to another. Typically, sound is slowest in gases, higher in liquids and higher still in solids. In air at ambient conditions sound travels at about 340 m/s, while in water it reaches about 1500 m/s and in iron more than 5000 m/s.
These differences are due to the way that a passing wave disturbs atoms and molecules. Thought of as hard spheres linked to one another with springs, the particles are knocked forward by their neighbours in the direction of sound propagation and in turn go on to nudge other neighbouring particles ahead of them. But this transmission is delayed by inertia, meaning that waves move faster when the particles are less massive.
Stiffer links mean less delay
However, stiffer links also mean less delay – each particle having to move less before it triggers the movement of its neighbour. This is why sound travels faster through iron than it does through water, for example.
Expressed mathematically, sound’s longitudinal speed in a material is equal to the square root of that material’s elastic modulus – which quantifies its resistance to compression – divided by its density.
In the latest research, Kostya Trachenko of Queen Mary University of London and colleagues at the University of Cambridge and the Russian Academy of Sciences’ Institute for High Pressure Physics set out to recast this formula in terms of fundamental constants. Their first step was to link a material’s bulk modulus with the energy that binds its atoms together, given that greater stiffness implies a higher binding energy. They then assumed that the latter term could be equated to the Rydberg energy, which is the characteristic binding energy in condensed matter.
Eye-catching formula
The resulting formula proved eye-catching, particularly when expressed in terms of the fine-structure constant – which sets the strength of fundamental electromagnetic interactions – and then written specifically as an upper limit on the speed of sound. The upper limit comes about when the mass of the atoms in question is the lowest mass possible – that of the hydrogen atom. In that case, the velocity of sound can simply be expressed in terms of the proton-to-electron mass ratio (inverted, halved and square-rooted), the fine-structure constant and the speed of light in a vacuum.
Inserting the relevant numbers into their formula, the researchers worked out that the highest possible speed of sound in solids and liquids (exposed to moderate pressures) comes in at a little over 36,000 m/s. That is still nearly 10,000 times slower than light’s upper limit but about twice as high as the fastest ever recorded sound wave – which stands at around 18,000 m/s and obtained in (very stiff) diamond.
To establish whether their equation is broadly in line with measured velocities, the researchers compared its predictions against the experimentally obtained speed of sound in 36 different elemental solids. To do so they used a log-log plot to show how these speeds vary with the solids’ atomic mass and on the same graph drew the straight sloping line generated by their equation – which terminates at the high end with hydrogen. They conclude that the experimental data points more or less follow their sloping line, even if a coefficient they dropped to simplify their equation means that not all are that close.
Metallic hydrogen
As an additional check on their work, Trachenko’s team used density functional theory to calculate the speed of sound through metallic hydrogen from first principles. When exposed to very high pressures, hydrogen becomes a molecular solid, and at pressures above about 400 GPa it is predicted then to become an atomic metal. It is this metallic state that should hold the speed record. Modelling hydrogen in these conditions, they found that sound should propagate at up to 35,000 m/s – faster than in any other material, but still below their upper limit.
This work follows similar research that Trachenko and fellow group member Vadim Brazhkin published earlier this year, which revealed a universal lower limit on viscosity expressed in terms of the proton-to-electron mass ratio and Planck’s constant. By incorporating the fine-structure constant, they ended up with an expression containing two fundamental constants whose fine tuning yields a stable proton and also allows stars to ignite and produce heavier elements, enabling, as they put it, “the existence of solids and liquids where sound can propagate”.
Kamran Behnia of PSL University in Paris describes the work as “simultaneously simple and deep”. He says he had not expected to be able to work out the rough speed of sound in a particular material “by hand-waving arguments” – particularly, he adds, when the resulting formula involves only fundamental constants. As he points out, quantum mechanics is not needed to explain the propagation of sound – even if quantum mechanics is what makes the solid state possible. “This is why the main message of this paper comes as a surprise,” he says.
The research is described in Science Advances.


physicsworld--2020-10-09--Searching for microfibres in the snow, differential equations make the world go round, Isaac Newton

Searching for microfibres in the snow, differential equations make the world go round, Isaac Newton first edition found while house clearing - Physics World

I grew up in Canada , which has two things in abundance : electric clothes dryers and snow .
So , I was immediately drawn to a paper in PLOS ONE by Kirsten Kapp and Rachael Miller that quantifies the number of microfibres emitted by tumble dryers by extracting fibres from snow nearby to dryer exhaust vents .
Their experiments were done in two snowy locations – Idaho and Vermont – using two different models of domestic dryer .
Kapp and Miller began their experiment with two pink polyester fleece blankets that were soaked and then placed in the dryers @ @ @ @ @ @ @ avoid introducing extra variables to the experiment .
After the blankets were dried , the surface layer of snow was gathered from a dozen or so different locations near the dryer vents .
The snow was then melted , and the fibres counted .
The duo found that the greatest concentration of microfibres were within about 1.5 m of the vents .
However , several locations about 9 m from the vents also had significant numbers of microfibres .
There is growing concern about microfibre pollution – and it is already well known @ @ @ @ @ @ @ a major source of microfibres in the environment .
“ The goal of this study was to break the story about dryers and microfibre emissions , rather than answer all the questions , ” says Miller .
“ Our intent is that these data now inspire researchers to investigate exactly what factors concerning dryer design , installation and settings increase or reduce shedding , inspire the white goods industry to include dryers in their discussions about microfibre pollution , and educate consumers about the potential effects that dryer use has on our environment.
@ @ @ @ @ @ @ think of anything that is more relevant to understanding how the world works than differential equations.
” So says the physicist Sabine Hossenfelder in the introduction to her latest video “ What are differential equations and how do they work ?
” which you can watch above .
Although Isaac Newton developed calculus – which underpins differential equations – our modern form of calculus is largely absent from his ground-breaking Mathematical Principles of Natural Philosophy .
A rare first edition of the book printed in 1729 has been sold at auction for £22,000 @ @ @ @ @ @ @ discovered during a lockdown clear-out at a house in South Wales .
“ It was on their shelves and they were looking for things to sell while they were in lockdown , ” says Chris Albury of Dominic Winter Auctioneers in Cirencester , who according to the BBC “ almost fell off ” his chair when he realized it was “ the greatest work of science in the English language ” .

Snowy scene: the location in Vermont where the distribution of microfibres in snow was measured. (Courtesy: Rachael Miller)
I grew up in Canada, which has two things in abundance: electric clothes dryers and snow. So, I was immediately drawn to a paper in PLOS ONE by Kirsten Kapp and Rachael Miller that quantifies the number of microfibres emitted by tumble dryers by extracting fibres from snow nearby to dryer exhaust vents. Their experiments were done in two snowy locations – Idaho and Vermont – using two different models of domestic dryer.
Kapp and Miller began their experiment with two pink polyester fleece blankets that were soaked and then placed in the dryers. The blankets were not washed to avoid introducing extra variables to the experiment. After the blankets were dried, the surface layer of snow was gathered from a dozen or so different locations near the dryer vents. The snow was then melted, and the fibres counted.
The duo found that the greatest concentration of microfibres were within about 1.5 m of the vents. However, several locations about 9 m from the vents also had significant numbers of microfibres.
There is growing concern about microfibre pollution – and it is already well known that wastewater from clothes washing machines is a major source of microfibres in the environment. “The goal of this study was to break the story about dryers and microfibre emissions, rather than answer all the questions,” says Miller. “Our intent is that these data now inspire researchers to investigate exactly what factors concerning dryer design, installation and settings increase or reduce shedding, inspire the white goods industry to include dryers in their discussions about microfibre pollution, and educate consumers about the potential effects that dryer use has on our environment.”
“I find it hard to think of anything that is more relevant to understanding how the world works than differential equations.” So says the physicist Sabine Hossenfelder in the introduction to her latest video “What are differential equations and how do they work?” which you can watch above.
Although Isaac Newton developed calculus – which underpins differential equations – our modern form of calculus is largely absent from his ground-breaking Mathematical Principles of Natural Philosophy. A rare first edition of the book printed in 1729 has been sold at auction for £22,000. Incredibly, the two-volume edition was discovered during a lockdown clear-out at a house in South Wales.
“It was on their shelves and they were looking for things to sell while they were in lockdown,” says Chris Albury of Dominic Winter Auctioneers in Cirencester, who according to the BBC “almost fell off” his chair when he realized it was “the greatest work of science in the English language”.


physicsworld--2020-10-09--Raining on the parade of self-driving cars - Physics World

Autonomous vehicles ( AVs ) are supposed to be the future .
So far , though , much of the work involved in building that future has focused on places like California and Arizona , where rain is rare and roads are wide and spacious .
How , then , will AVs cope in the harsher conditions of northern Europe ?
For Patrick Sachon , the question is more than hypothetical .
As a scientist working in business development at the Met Office , Sachon is trying to understand whether the sensors that AVs use to navigate can do their @ @ @ @ @ @ @ famously unsettled weather .
If the answer is “ no ” – or , more likely , a provisional “ yes ” that depends on weather conditions remaining within a certain safety envelope – then he and his colleagues aim to suggest improvements and explain to regulators what safe use looks like .
Speaking as part of a webinar series organized by the National Physical Laboratory , Sachon noted that the Met Office ( the UK ’ s national weather service ) has collaborated with partners in the road transport sector for years @ @ @ @ @ @ @ on understanding what roads will be like to drive on , ” he explains .
While the Met Office ’ s publicly-funded forecasts are ( usually ) good enough for citizens to decide whether they need to pack an umbrella , the Highways Agency and local authorities need far more detailed information to help them deploy assets such as gritters , snowploughs and maintenance crews in an optimal way .
The Met Office ’ s experience of providing such information is useful for AVs , Sachon says , because such vehicles may require @ @ @ @ @ @ @ he puts , it , the “ structure of precipitation ” varies a lot during thunderstorms or heavy showers .
While some areas experience high rain rates , others nearby remain relatively dry .
And if AV sensors work fine in ordinary rain , but not when it ’ s chucking it down , then the basic , publicly-available weather forecasts won ’ t be enough to keep motorists safe .
As Sachon sees it , the key will be to develop vehicle sensors that work alongside weather sensors .
The joint information @ @ @ @ @ @ @ enable regulators and manufacturers to determine exactly how well – and how safely – an AV ’ s sensors will handle a given set of conditions .
Such information will be helpful to the Met Office , too , Sachon adds , because vehicle-based weather sensors are a bit like miniature weather stations .
For example , if Met Office scientists see that an AV ’ s windscreen wipers are on , they ’ ll know that moisture in the atmosphere is making it down to ground level – something that weather satellites @ @ @ @ @ @ @ scientists can then modify their forecasts accordingly , to more accurately reflect local driving conditions .
When asked which weather conditions are most challenging to AV sensors , Sachon began by reminding listeners that human-operated vehicles have drawbacks of their own .
“ [ Artificial intelligence ] won ’ t do the stupid things we do when we drive , ” he said .
“ You can eliminate quite a lot of risks.
” With that caveat , though , he acknowledged that AV sensors struggle when precipitation changes phase .
While rain @ @ @ @ @ @ @ their own , he said , “ the transition between phases can be quite a problem ” .
Since the UK ’ s weather often hovers between fog , mist , drizzle , rain and snow , would-be AV purchasers in these islands may be in for a long wait .
Another challenge is that hyper-local weather forecasts are not cheap , and it is far from clear who within the AV sector would pay for them .
The equivalent service in aviation , Sachon notes , is paid for via a levy @ @ @ @ @ @ @ airspace , with a small fraction of that levy going to the Met Office .
In ground transport , however , the focus has traditionally been around keeping roads clear of ice and snow , and the burden of payment has fallen on local authorities rather than individual motorists .
Whether any government – local or national – will take on those costs for the sake of an ( initially ) small number of AV users is , he suggests , an open question .

Unsettled forecast The UK's messy, complex weather presents a challenge for autonomous vehicles. (Courtesy: iStock/trendobjects)
Autonomous vehicles (AVs) are supposed to be the future. So far, though, much of the work involved in building that future has focused on places like California and Arizona, where rain is rare and roads are wide and spacious. How, then, will AVs cope in the harsher conditions of northern Europe?
For Patrick Sachon, the question is more than hypothetical. As a scientist working in business development at the Met Office, Sachon is trying to understand whether the sensors that AVs use to navigate can do their job adequately in the UK’s famously unsettled weather. If the answer is “no” – or, more likely, a provisional “yes” that depends on weather conditions remaining within a certain safety envelope – then he and his colleagues aim to suggest improvements and explain to regulators what safe use looks like.
Speaking as part of a webinar series organized by the National Physical Laboratory, Sachon noted that the Met Office (the UK’s national weather service) has collaborated with partners in the road transport sector for years. “We’re always working on understanding what roads will be like to drive on,” he explains. While the Met Office’s publicly-funded forecasts are (usually) good enough for citizens to decide whether they need to pack an umbrella, the Highways Agency and local authorities need far more detailed information to help them deploy assets such as gritters, snowploughs and maintenance crews in an optimal way.
The Met Office’s experience of providing such information is useful for AVs, Sachon says, because such vehicles may require similar micro-forecasts to operate safely. As he puts, it, the “structure of precipitation” varies a lot during thunderstorms or heavy showers. While some areas experience high rain rates, others nearby remain relatively dry. And if AV sensors work fine in ordinary rain, but not when it’s chucking it down, then the basic, publicly-available weather forecasts won’t be enough to keep motorists safe.
As Sachon sees it, the key will be to develop vehicle sensors that work alongside weather sensors. The joint information from both types of sensors will then enable regulators and manufacturers to determine exactly how well – and how safely – an AV’s sensors will handle a given set of conditions. Such information will be helpful to the Met Office, too, Sachon adds, because vehicle-based weather sensors are a bit like miniature weather stations. For example, if Met Office scientists see that an AV’s windscreen wipers are on, they’ll know that moisture in the atmosphere is making it down to ground level – something that weather satellites don’t necessarily show. The scientists can then modify their forecasts accordingly, to more accurately reflect local driving conditions.
When asked which weather conditions are most challenging to AV sensors, Sachon began by reminding listeners that human-operated vehicles have drawbacks of their own. “[Artificial intelligence] won’t do the stupid things we do when we drive,” he said. “You can eliminate quite a lot of risks.” With that caveat, though, he acknowledged that AV sensors struggle when precipitation changes phase. While rain and snow are not so difficult on their own, he said, “the transition between phases can be quite a problem”.
Since the UK’s weather often hovers between fog, mist, drizzle, rain and snow, would-be AV purchasers in these islands may be in for a long wait. Another challenge is that hyper-local weather forecasts are not cheap, and it is far from clear who within the AV sector would pay for them. The equivalent service in aviation, Sachon notes, is paid for via a levy on all airlines that fly through UK airspace, with a small fraction of that levy going to the Met Office. In ground transport, however, the focus has traditionally been around keeping roads clear of ice and snow, and the burden of payment has fallen on local authorities rather than individual motorists. Whether any government – local or national – will take on those costs for the sake of an (initially) small number of AV users is, he suggests, an open question.


physicsworld--2020-10-09--Path of least resistance - Physics World

Rosemary Teague is a trainee teacher on the physics PGCE programme at University College London “ What will you do with a physics degree ?
” asked my aunts and uncles when I excitedly told them I was going to study the subject at Imperial College in London , as an undergraduate .
Well , I thought , I ’ m going to be a physicist .
Back then , my understanding of what a career in physics entailed was not far beyond that of my family – I knew it as an academic pursuit and pictured myself , 30 @ @ @ @ @ @ @ discoveries in renewable energy .
Really , though , I wasn ’ t thinking that far ahead .
I was thinking about the first four years : leaving home , making friends , and learning about the laws of the universe .
And that ’ s what I did .
My undergrad years were filled with lectures , labs and dancing .
As a self-proclaimed “ country bumpkin ” who grew up in Gloucestershire , I took to London life relatively well , making life-long friends and taking every opportunity the city presented @ @ @ @ @ @ @ a similar fashion , either travelling or earning money to travel by teaching at summer camps .
I spent my third year in Valencia , Spain , as part of the Erasmus programme , and surprised myself by choosing a computational research project .
At this point I noticed my friends and peers were already considering life after our degrees .
We were on a four-year programme , so the upcoming summer was our last chance to get some work experience before applying for graduate jobs .
I didn ’ t spend much @ @ @ @ @ @ @ was confident that I wanted to stay in academia , and follow that linear path .
So , while my friends were off earning big bucks in the City , I crashed with a school friend for a couple of months and worked in a practical lab at the University of Bristol .
While the city and research group were lovely , it confirmed that I ’ m more suited to a computer than optical mounts .
Always one to be prepared , I started looking into PhD programmes at the beginning of @ @ @ @ @ @ @ centres for doctoral training ( CDTs ) , which tend to have a more interdisciplinary focus , and incorporate a Master ’ s qualification into a full PhD programme .
CDTs also complement study with opportunities to develop outreach and other career skills .
Among standard PhD applications , I applied to several CDTs including one on the theory and simulation of materials at Imperial .
When I accepted this offer , I was excited about both the course and staying in London to take the next step in my personal life by @ @ @ @ @ @ @ would be starting a more traditional PhD in ultrafast lasers , also at Imperial .
Not long after starting the MSc , reality hit and my life started to get a bit less rosy .
I struggled with impostor syndrome , as many postgraduate students do , and would work long hours to prove that I deserved the place .
I also , crucially , wasn ’ t giving myself the time or space to grieve a close and unexpected loss in my partner ’ s family .
I started to have panic @ @ @ @ @ @ @ , I have a strong network of family and friends who encouraged me to take a break , despite warnings from the university of the workload that would be waiting on my return .
I escaped to my parents ’ home , was prescribed antidepressants and arranged to start cognitive behavioural therapy ( CBT ) sessions back in London .
These had an incredible impact and gave me a new perspective on my work–life balance .
I realized how much I hated the pressure and competition around working late and , instead of @ @ @ @ @ @ @ making the decision to leave university before starting the PhD part of the course .
This was an incredibly tough choice – while easier than if I was on a traditional PhD path , without my MSc graduation as an obtainable “ end-point ” , it felt like I was giving up , quitting on academia and failing to meet my ambitions .
So what then ?
I was still living in London and paying rent , so I desperately needed an income .
I didn ’ t have the luxury of time @ @ @ @ @ @ @ wanted and instead applied for anything and everything I could .
A recruiter got in touch via LinkedIn and arranged an interview at Ocado Technology , the online supermarket .
Two and a half months after handing in my MSc dissertation , I started working for Ocado as a cloud infrastructure engineer .
It was a good job that paid well , but I wasn ’ t passionate about it and the hour-and-a-quarter commute quickly took its toll .
After six months , in a move that I ’ m still not sure @ @ @ @ @ @ @ % of my salary for a job in the outreach and engagement department at the Institute of Physics [ which publishes Physics World ] .
This was in May 2019 , and it was the right decision for me – I hadn ’ t been this happy for a long time .
More recently I have been considering what it is that I want out of a career .
I know that collaborating and working with others is important to me , and whatever I do must be physics-focused .
By assessing my @ @ @ @ @ @ @ what I truly enjoy , I narrowed down my options to a future career in one of three areas : public outreach and engagement ; teaching ; or academic publishing .
Once I considered the skills these roles need and the opportunities they could offer ( see graphic above ) I realized that for me right now , a career in teaching is the most rewarding path , helping others to see the joys of physics while also developing myself .
With this in mind , I applied for teacher training courses , @ @ @ @ @ @ @ my PGCE last month .
By sharing my story , I hope it will show that there are many ways to start a career and that it ’ s okay to take time for yourself .
My path recently has been far from linear and strongly supported by people I love .
I am looking forward to seeing how it twists and turns in the years to come .
Amber Yallop is a new trainee on a graduate scheme with MBDA , after completing her BSc in physics at the University of East @ @ @ @ @ @ @ not the most traditional or straightforward .
It began in September 2016 when I left my hometown of Norwich , UK , to follow my dream of a degree in astrophysics , which has always been my specific area of interest .
Although I loved my course , I struggled in the first few months , due to some personal circumstances that were further exacerbated by living away from home .
By December 2016 I made the very difficult decision to drop out of my course and return home .
At this point @ @ @ @ @ @ @ return to higher education .
I took a job at a local high school , where I supported students with special educational needs .
The role was challenging , but also incredibly rewarding , and I thoroughly enjoyed my seven months at the school .
During my time there , however , I heard that a local university – the University of East Anglia ( UEA ) – was going to launch a new physics degree , starting in September 2017 .
I had previously considered teaching as a career , but in @ @ @ @ @ @ @ realized that I much preferred working on a personal , one-to-one basis with the students and I wouldn ’ t get the same level of involvement and intervention as a class teacher .
While I loved the job , I still had high aspirations and the physics course at UEA came along at the right time and in the right place .
I chose to take the opportunity , and applied to the course .
I was offered a place and decided to give university a second attempt , but this time living @ @ @ @ @ @ @ for me and despite further setbacks during my three years , including being diagnosed with epilepsy , I managed to stay on track and obtain a first-class degree .
During my BSc , I volunteered at Institute of Physics outreach events , including a day at the Royal Norfolk Show , demonstrating and explaining hands-on physics experiments to the public , and also took part in the Norwich Science Festival .
In my second year at university , I successfully applied to be the IOP campus ambassador for East Anglia .
This role @ @ @ @ @ @ @ , including organizing events like a public lecture with BBC Stargazing Live ’ s Mark Thompson .
This was a very popular event with both students and members of the public .
I was also lucky enough to represent East Anglia on the IOP ’ s Student Community Panel for the final two years of my degree .
This involved travelling across the UK and Ireland to meet other regional representatives .
We addressed issues facing physics students across the country , and supported the IOP with student events .
My proudest achievement @ @ @ @ @ @ @ in sponsorship for PLANCKS 2020 , an annual physics competition for students around the world , hosted by the International Association of Physics Students .
Each country holds its own preliminary round , with the winning teams progressing to the final competition , which takes place in a different country each year .
The 2020 final was scheduled to be held in May in London , but was postponed as a result of COVID-19 .
I have recently relocated to Stevenage to begin a “ Hardware in the Loop ” graduate scheme with @ @ @ @ @ @ @ is a two-year programme with a permanent position on completion .
It includes training , development , outreach and extracurricular opportunities .
I am looking forward to applying the knowledge and skills learnt through my degree to the workplace , and I ’ m excited to see where this next chapter of my life will take me .

Physics World. Members of the Institute of Physics can enjoy the full issue Taken from the October 2020 issue of. Members of the Institute of Physics can enjoy the full issue via the Physics World app
Graduate student Rosemary Teague and undergraduate Amber Yallop share their non-traditional degree pathways, some difficult choices they made along the way, and what a future in physics looks like for them now
Nonlinear narrative Rosemary Teague left her PhD part-way through to investigate other careers in physics. (Courtesy: IOP/Lucy Kinghan)
Rosemary Teague is a trainee teacher on the physics PGCE programme at University College London
“What will you do with a physics degree?” asked my aunts and uncles when I excitedly told them I was going to study the subject at Imperial College in London, as an undergraduate. Well, I thought, I’m going to be a physicist. Back then, my understanding of what a career in physics entailed was not far beyond that of my family – I knew it as an academic pursuit and pictured myself, 30 years on, at the forefront of discoveries in renewable energy. Really, though, I wasn’t thinking that far ahead. I was thinking about the first four years: leaving home, making friends, and learning about the laws of the universe.
And that’s what I did. My undergrad years were filled with lectures, labs and dancing. As a self-proclaimed “country bumpkin” who grew up in Gloucestershire, I took to London life relatively well, making life-long friends and taking every opportunity the city presented. I spent my summer holidays in a similar fashion, either travelling or earning money to travel by teaching at summer camps. I spent my third year in Valencia, Spain, as part of the Erasmus programme, and surprised myself by choosing a computational research project.
At this point I noticed my friends and peers were already considering life after our degrees. We were on a four-year programme, so the upcoming summer was our last chance to get some work experience before applying for graduate jobs. I didn’t spend much time thinking about this myself as I was confident that I wanted to stay in academia, and follow that linear path. So, while my friends were off earning big bucks in the City, I crashed with a school friend for a couple of months and worked in a practical lab at the University of Bristol. While the city and research group were lovely, it confirmed that I’m more suited to a computer than optical mounts.
Always one to be prepared, I started looking into PhD programmes at the beginning of my final year. I soon discovered centres for doctoral training (CDTs), which tend to have a more interdisciplinary focus, and incorporate a Master’s qualification into a full PhD programme. CDTs also complement study with opportunities to develop outreach and other career skills. Among standard PhD applications, I applied to several CDTs including one on the theory and simulation of materials at Imperial. When I accepted this offer, I was excited about both the course and staying in London to take the next step in my personal life by moving in with my partner – he would be starting a more traditional PhD in ultrafast lasers, also at Imperial.
I struggled with impostor syndrome and would work long hours to prove that I deserved the place
Not long after starting the MSc, reality hit and my life started to get a bit less rosy. I struggled with impostor syndrome, as many postgraduate students do, and would work long hours to prove that I deserved the place. I also, crucially, wasn’t giving myself the time or space to grieve a close and unexpected loss in my partner’s family. I started to have panic attacks and increasingly depressive thoughts. Luckily, I have a strong network of family and friends who encouraged me to take a break, despite warnings from the university of the workload that would be waiting on my return. I escaped to my parents’ home, was prescribed antidepressants and arranged to start cognitive behavioural therapy (CBT) sessions back in London. These had an incredible impact and gave me a new perspective on my work–life balance.
I realized how much I hated the pressure and competition around working late and, instead of dismissing advice, I heeded it, making the decision to leave university before starting the PhD part of the course. This was an incredibly tough choice – while easier than if I was on a traditional PhD path, without my MSc graduation as an obtainable “end-point”, it felt like I was giving up, quitting on academia and failing to meet my ambitions.
So what then? I was still living in London and paying rent, so I desperately needed an income. I didn’t have the luxury of time to consider what sort of job I wanted and instead applied for anything and everything I could. A recruiter got in touch via LinkedIn and arranged an interview at Ocado Technology, the online supermarket. Two and a half months after handing in my MSc dissertation, I started working for Ocado as a cloud infrastructure engineer. It was a good job that paid well, but I wasn’t passionate about it and the hour-and-a-quarter commute quickly took its toll.
Exploring her options To help her decide what career pathway to follow, Rosemary Teague put together some data on her current expertise, as well as the proficiencies she would like to develop. She then matched these to three possible careers, with teaching emerging as the best path. (Click to enlarge)
After six months, in a move that I’m still not sure my parents understood, I sacrificed 30% of my salary for a job in the outreach and engagement department at the Institute of Physics [which publishes Physics World]. This was in May 2019, and it was the right decision for me – I hadn’t been this happy for a long time. More recently I have been considering what it is that I want out of a career. I know that collaborating and working with others is important to me, and whatever I do must be physics-focused.
By assessing my own skills, and thinking critically about what I truly enjoy, I narrowed down my options to a future career in one of three areas: public outreach and engagement; teaching; or academic publishing. Once I considered the skills these roles need and the opportunities they could offer (see graphic above) I realized that for me right now, a career in teaching is the most rewarding path, helping others to see the joys of physics while also developing myself. With this in mind, I applied for teacher training courses, and am incredibly excited as I began my PGCE last month.
By sharing my story, I hope it will show that there are many ways to start a career and that it’s okay to take time for yourself. My path recently has been far from linear and strongly supported by people I love. I am looking forward to seeing how it twists and turns in the years to come.
On the right track Amber Yallop needed to find a university set-up that worked for her circumstances. (Courtesy: IOP)
Amber Yallop is a new trainee on a graduate scheme with MBDA, after completing her BSc in physics at the University of East Anglia, UK
My degree pathway was not the most traditional or straightforward. It began in September 2016 when I left my hometown of Norwich, UK, to follow my dream of a degree in astrophysics, which has always been my specific area of interest. Although I loved my course, I struggled in the first few months, due to some personal circumstances that were further exacerbated by living away from home. By December 2016 I made the very difficult decision to drop out of my course and return home.
At this point I was unsure if I would ever return to higher education. I took a job at a local high school, where I supported students with special educational needs. The role was challenging, but also incredibly rewarding, and I thoroughly enjoyed my seven months at the school. During my time there, however, I heard that a local university – the University of East Anglia (UEA) – was going to launch a new physics degree, starting in September 2017.
I had previously considered teaching as a career, but in my time working at the school I realized that I much preferred working on a personal, one-to-one basis with the students and I wouldn’t get the same level of involvement and intervention as a class teacher. While I loved the job, I still had high aspirations and the physics course at UEA came along at the right time and in the right place. I chose to take the opportunity, and applied to the course. I was offered a place and decided to give university a second attempt, but this time living at home. This worked much better for me and despite further setbacks during my three years, including being diagnosed with epilepsy, I managed to stay on track and obtain a first-class degree.
I decided to give university a second attempt, but this time living at home. This worked much better for me
During my BSc, I volunteered at Institute of Physics outreach events, including a day at the Royal Norfolk Show, demonstrating and explaining hands-on physics experiments to the public, and also took part in the Norwich Science Festival. In my second year at university, I successfully applied to be the IOP campus ambassador for East Anglia. This role massively improved my confidence and organizational skills, including organizing events like a public lecture with BBC Stargazing Live’s Mark Thompson. This was a very popular event with both students and members of the public.
I was also lucky enough to represent East Anglia on the IOP’s Student Community Panel for the final two years of my degree. This involved travelling across the UK and Ireland to meet other regional representatives. We addressed issues facing physics students across the country, and supported the IOP with student events. My proudest achievement in this role was raising over £1000 in sponsorship for PLANCKS 2020, an annual physics competition for students around the world, hosted by the International Association of Physics Students. Each country holds its own preliminary round, with the winning teams progressing to the final competition, which takes place in a different country each year. The 2020 final was scheduled to be held in May in London, but was postponed as a result of COVID-19.
I have recently relocated to Stevenage to begin a “Hardware in the Loop” graduate scheme with the European defence company MBDA. This is a two-year programme with a permanent position on completion. It includes training, development, outreach and extracurricular opportunities. I am looking forward to applying the knowledge and skills learnt through my degree to the workplace, and I’m excited to see where this next chapter of my life will take me.
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