physicsworld--2020-08-12--Quantum-inspired detection method generates high-quality OCT images - Physics World

A novel detection method for optical coherence tomography ( OCT ) achieves high-quality imaging at low light intensity .
The new OCT method was developed by a group of researchers from the University of Auckland in New Zealand and the Nicolaus Copernicus University in Poland .
Borrowing ideas for their detection mechanism from quantum optics , they describe in Optics Letters how the method can produce comparable results to standard OCT systems at very low light intensity levels ( around 10 pW ) .
OCT is a widely used medical imaging technique that can non-invasively obtain cross-sectional images of semi-translucent @ @ @ @ @ @ @ medical disciplines , including ophthalmology , cardiology and dermatology , where its resolution allows visualization of microscopic details .
It works by illuminating the tissue with broad-bandwidth visible or near-infrared light .
This light is scattered and reflected by the biological media and then captured and assessed using a spectroscopic detector .
OCT can provide images of tissue morphology at 1 µm resolution and it is now a common part of routine eye exams , where an ophthalmologist may recommend the scan to inspect the retina ’ s distinctive layers and rule out @ @ @ @ @ @ @ clinical setting , OCT is limited by the allowed intensity levels .
For example , the imposed safety levels for imaging the eye are 1.7 and 5 mW , at wavelengths of 800 and 1060 nm , respectively , constraints that can sometimes affect the fidelity of the obtained images .
A team led by Sylwia Kolenderska bypassed this limitation by using a superconducting single-photon detector ( SSPD ) instead of the standard OCT detector – an idea inspired by quantum optics , where SSPDs are used to study various properties of single @ @ @ @ @ @ @ low-power OCT systems , the team came up with the idea of using an SSPD while researching new OCT detection schemes .
As these sensors can detect single photons , the proposed setup uses a much smaller amount of light than a standard OCT system .
In fact , the required power is a few orders of magnitude smaller than clinically available counterparts .
To make the new detection scheme work , the team had to make a few changes to the original optical setup , which requires a way of discerning the @ @ @ @ @ @ @ the imaged object .
As they were now working in a single-photon detection regime , the researchers decided to couple the SSPD with a long ( 5 km ) fibre spool that induces a wavelength-dependent time delay .
In other words , different wavelengths of light will travel at different speeds down this fibre , enabling the SSPD to capture the light spectrum .
The team tested the new OCT setup using a 1550 nm pulsed light source to image two objects : a stack of different types of glass and a slice @ @ @ @ @ @ @ made up of three layers : quartz ( 50 µm thick ) , sapphire ( 460 µm thick ) and BK7 glass ( 500 µm thick ) , and it was used as a controlled test to understand how well the different layers can be discerned .
The slice of onion was used as a biological sample .
Both experiments resulted in good-quality images , comparable with images obtained by standard OCT systems , but using intensity levels five orders of magnitude lower .
The researchers point out that they observed artefacts in @ @ @ @ @ @ @ image features that , in this case , appear because the detection system is recording all types of interactions between photons inside the sample .
Artefact removal algorithms can be used to clean up the images and are straightforward to use when the imaged object has a well-defined structure , such as the stack of glass .
These artefacts become more problematic when dealing with biological samples , where the structure is highly heterogeneous and complicated .

Researchers Sylwia Kolenderska and Piotr Kolenderski are using single-photon detectors to enhance OCT. (Courtesy: Andrzej Romański, Sylwia Kolenderska)
A novel detection method for optical coherence tomography (OCT) achieves high-quality imaging at low light intensity. The new OCT method was developed by a group of researchers from the University of Auckland in New Zealand and the Nicolaus Copernicus University in Poland. Borrowing ideas for their detection mechanism from quantum optics, they describe in Optics Letters how the method can produce comparable results to standard OCT systems at very low light intensity levels (around 10 pW).
OCT is a widely used medical imaging technique that can non-invasively obtain cross-sectional images of semi-translucent materials. It has applications in several medical disciplines, including ophthalmology, cardiology and dermatology, where its resolution allows visualization of microscopic details. It works by illuminating the tissue with broad-bandwidth visible or near-infrared light. This light is scattered and reflected by the biological media and then captured and assessed using a spectroscopic detector.
OCT can provide images of tissue morphology at 1 µm resolution and it is now a common part of routine eye exams, where an ophthalmologist may recommend the scan to inspect the retina’s distinctive layers and rule out glaucoma or retinal diseases.
In a clinical setting, OCT is limited by the allowed intensity levels. For example, the imposed safety levels for imaging the eye are 1.7 and 5 mW, at wavelengths of 800 and 1060 nm, respectively, constraints that can sometimes affect the fidelity of the obtained images. A team led by Sylwia Kolenderska bypassed this limitation by using a superconducting single-photon detector (SSPD) instead of the standard OCT detector – an idea inspired by quantum optics, where SSPDs are used to study various properties of single photons.
One photon at a time…
Leading the way towards high-fidelity low-power OCT systems, the team came up with the idea of using an SSPD while researching new OCT detection schemes. As these sensors can detect single photons, the proposed setup uses a much smaller amount of light than a standard OCT system. In fact, the required power is a few orders of magnitude smaller than clinically available counterparts.
To make the new detection scheme work, the team had to make a few changes to the original optical setup, which requires a way of discerning the different wavelengths of light being reflected from the imaged object. As they were now working in a single-photon detection regime, the researchers decided to couple the SSPD with a long (5 km) fibre spool that induces a wavelength-dependent time delay. In other words, different wavelengths of light will travel at different speeds down this fibre, enabling the SSPD to capture the light spectrum.
…yields high-quality images
The team tested the new OCT setup using a 1550 nm pulsed light source to image two objects: a stack of different types of glass and a slice of onion. The glass stack was made up of three layers: quartz (50 µm thick), sapphire (460 µm thick) and BK7 glass (500 µm thick), and it was used as a controlled test to understand how well the different layers can be discerned. The slice of onion was used as a biological sample. Both experiments resulted in good-quality images, comparable with images obtained by standard OCT systems, but using intensity levels five orders of magnitude lower.
The researchers point out that they observed artefacts in the reconstructed images. These are unwanted image features that, in this case, appear because the detection system is recording all types of interactions between photons inside the sample. Artefact removal algorithms can be used to clean up the images and are straightforward to use when the imaged object has a well-defined structure, such as the stack of glass. These artefacts become more problematic when dealing with biological samples, where the structure is highly heterogeneous and complicated.


physicsworld--2020-08-12--Maximizing QA accuracy and efficiency with RadCalc in a challenging environment - Physics World

Participants will learn how RadCalc ’ s 3D packages can improve accuracy , efficiency and safety in the QA process @ @ @ @ @ remote location .
The webinar , presented by Dana Cooper , will help the audience @ @ @ @ @ workflow of the RadCalc 3D .
• Types of plans for RadCalc in a challenging @ @ @ @ @ .
Dana Cooper is a certified medical dosimetrist/technical sales representative with LifeLine Software , Inc @ @ @ @ @ Group .
She has more than 25 years of experience in radiation oncology , having @ @ @ @ @ therapist , dosimetrist and department manager .
Dana joined LSI in 2016 and has been @ @ @ @ @ software that increases productivity and safety ever since .

Explore the ways in which today’s world relies on AI, and ponder how this technology might shape the world of tomorrow


physicsworld--2020-08-12--First ‘open flavour’ tetraquark is spotted by LHCb at CERN - Physics World

The first tetraquark composed of four quarks of different flavours has been discovered by physicists working on the LHCb experiment at CERN .
Dubbed X ( 2900 ) , the “ open flavour ” tetraquark has a mass of about 2.9 GeV/c2 and has been spotted in two spin states .
The tetraquark was made by smashing protons together at the Large Hardron Collider ( LHC ) to produce B mesons – and then searching the B meson decay products for signs of new particles .
While LHCb physicists are not completely certain about the nature of the particle – @ @ @ @ @ @ @ name – they believe it contains four quarks : anticharm , antistrange , up and down .
Because the tetraquark does not contain a quark-antiquark pair of the same flavour , no quark flavours are hidden and therefore the tetraquark is described as open flavour .
Hadrons are made of two or more bound quarks or antiquarks .
Mesons comprise a quark and antiquark , whereas baryons such as protons and neutrons comprise three quarks .
However , nature does not stop at three quarks and several tetraquarks ( two quarks and two @ @ @ @ @ @ @ and an antiquark ) have been discovered .
Before the discovery of X ( 2900 ) , all known tetraquarks contained at least one charm-anticharm or beauty-antibeauty quark pair .
According to LHCb physicist Tim Gershon of the University of Warwick , an open-charm/open-strange tetraquark such as X ( 2900 ) had been considered possible .
However , no-one had made predictions of this particular hadron , so the discovery took the LHCb team by surprise .
Because it only contains one heavy quark ( the anticharm ) , X ( 2900 ) @ @ @ @ @ @ @ other tetraquarks .
This , says , Gershon makes it easier to produce at the LHC than its heavier cousins .
However , he points out that tetraquarks containing charm/anticharm pairs are relatively easy to observe because they decay to a final state that contains the J/psi meson – which itself has a very clean experimental signature .
“ Open flavour tetraquarks will tend to have less clean experimental signatures , and it is only due to the unique design , and incredible performance , of the LHCb detector that we are able @ @ @ @ @ @ @ explains Gershon .
Gershon is hopeful that X ( 2900 ) could shed light on an important mystery of tetraquarks – how the four quarks arrange themselves internally .
This is defined by strong-force interactions between quarks , which are extremely difficult to calculate .
One possibility is that all the quarks and antiquarks are tightly bound together .
Another is that they are arranged as two quark–antiquark pairs loosely bound in a structure that resembles a molecule made from two mesons .
Gershon points out that the mass of X ( 2900 @ @ @ @ @ @ @ the masses of an excited D meson and an excited kaon – which together have the same quark content as X ( 2900 ) .
This could point towards the molecular model , but Gershon says it is too early to draw any conclusions .
Just last month , physicists working on the LHCb experiment discovered the first tetraquark that comprises all charm and anticharm quarks .
As for more tetraquark discoveries , Gershon says , “ There are many possible avenues of exploration , and I am certain that there is more @ @ @ @ @ @ @ treasure trove of data !
The problem is that it is hard to know which directions are more likely to yield discoveries , so I can not say how long we will need to wait.
” • Listen to Tim Gershon and his LHCb colleague Greig Cowan talk about tetraquarks and pentaquarks on the Physics World Weekly podcast .
The pair have also written the free-to-read ebook Tetraquarks and Pentaquarks .

No pairs: the first ‘open flavour’ tetraquark has been spotted at CERN (Courtesy: Shutterstock/paul_june)
The first tetraquark composed of four quarks of different flavours has been discovered by physicists working on the LHCb experiment at CERN. Dubbed X(2900), the “open flavour” tetraquark has a mass of about 2.9 GeV/c2 and has been spotted in two spin states. The tetraquark was made by smashing protons together at the Large Hardron Collider (LHC) to produce B mesons – and then searching the B meson decay products for signs of new particles.
While LHCb physicists are not completely certain about the nature of the particle – hence the “X” in the name – they believe it contains four quarks: anticharm, antistrange, up and down. Because the tetraquark does not contain a quark–antiquark pair of the same flavour, no quark flavours are hidden and therefore the tetraquark is described as open flavour.
Hadrons are made of two or more bound quarks or antiquarks. Mesons comprise a quark and antiquark, whereas baryons such as protons and neutrons comprise three quarks. However, nature does not stop at three quarks and several tetraquarks (two quarks and two antiquarks) and pentaquarks (four quarks and an antiquark) have been discovered.
No predictions
Before the discovery of X(2900), all known tetraquarks contained at least one charm–anticharm or beauty–antibeauty quark pair. According to LHCb physicist Tim Gershon of the University of Warwick, an open-charm/open-strange tetraquark such as X(2900) had been considered possible. However, no-one had made predictions of this particular hadron, so the discovery took the LHCb team by surprise.
Because it only contains one heavy quark (the anticharm), X(2900) has a relatively low mass compared to other tetraquarks. This, says, Gershon makes it easier to produce at the LHC than its heavier cousins. However, he points out that tetraquarks containing charm/anticharm pairs are relatively easy to observe because they decay to a final state that contains the J/psi meson – which itself has a very clean experimental signature.
“Open flavour tetraquarks will tend to have less clean experimental signatures, and it is only due to the unique design, and incredible performance, of the LHCb detector that we are able to make this latest discovery,” explains Gershon.
Mesonic molecules?
Gershon is hopeful that X(2900) could shed light on an important mystery of tetraquarks – how the four quarks arrange themselves internally. This is defined by strong-force interactions between quarks, which are extremely difficult to calculate. One possibility is that all the quarks and antiquarks are tightly bound together. Another is that they are arranged as two quark–antiquark pairs loosely bound in a structure that resembles a molecule made from two mesons.
Gershon points out that the mass of X(2900) is similar to the sum of the masses of an excited D meson and an excited kaon – which together have the same quark content as X(2900). This could point towards the molecular model, but Gershon says it is too early to draw any conclusions.
Just last month, physicists working on the LHCb experiment discovered the first tetraquark that comprises all charm and anticharm quarks. As for more tetraquark discoveries, Gershon says, “There are many possible avenues of exploration, and I am certain that there is more to be found in LHCb’s treasure trove of data! The problem is that it is hard to know which directions are more likely to yield discoveries, so I cannot say how long we will need to wait.”
Listen to Tim Gershon and his LHCb colleague Greig Cowan talk about tetraquarks and pentaquarks on the Physics World Weekly podcast. The pair have also written the free-to-read ebook Tetraquarks and Pentaquarks.


physicsworld--2020-08-12--Light waves steer electron beams thanks to whispering gallery effect - Physics World

Visitors to Saint Paul ’ s in London are often astonished by the cathedral ’ s whispering gallery , where words spoken in a whisper along the curving wall of the dome can be heard anywhere along that same wall – including the opposite side of the circular walkway , some 33 metres away .
This “ whispering gallery effect ” is possible because sound runs so easily and smoothly around the dome ’ s circumference , and variations of it occur wherever waves can travel nearly perfectly around a structure .
Researchers at the University of Göttingen in Germany @ @ @ @ @ @ @ to control the beam of an electron microscope using light .
As well as being of fundamental importance , they say that the work might lead to novel technologies for nanoscale sensing and microscopy .
In their work , researchers led by Ofer Kfir and Claus Ropers illuminated small glass spheres with laser light that was trapped in an optical whispering-gallery mode , meaning that it was confined to the surface of the sphere by total internal reflection .
Analogous to the acoustic example , the light wave travels around the sphere ’ @ @ @ @ @ @ @ researchers then passed a beam of electrons in a transmission electron microscope near the edge of a sphere .
When they measured the distribution of electron velocities using the microscope , they discovered that the electrons had exchanged large amounts of energy with the electric field of the laser light – roughly 10 times more energy , in fact , than any such exchange previously measured in an electron microscope .
The strength of the electron-light interaction comes from two contributions , Kfir explains .
First , the whispering-gallery optical modes make it @ @ @ @ @ @ @ up a stronger wave .
Second , the velocity of the light wave on the glass sphere matches that of the electron , running at 70 % of the speed of light .
This matching changes the quantum state of the electron ( see image ) .
The coupling that occurs between an electron and the light ’ s electric field can be thought of as the acceleration ( or deceleration ) of the electron by the light field , he tells Physics World .
“ In the same way a surfer matches @ @ @ @ @ @ @ best use its energy , an electron ‘ riding ’ the light wave is therefore either purely accelerated or purely decelerated over a substantial distance , ” he says .
“ Indeed , in our study , we observed that individual electrons had picked up or given away the energy of hundreds of photons.
” As well as being of fundamental interest , the researchers say their findings could bring a greater functionality to electron microscopy – an indispensable characterization tool for research in many scientific disciplines as well as in industry .
@ @ @ @ @ @ @ light to control the electrons ’ quantum state in transmission electron microscopes would open up a range of novel imaging and spectroscopy techniques , making it possible to inspect the optical properties of materials with resolutions down to the atomic scale .
The researchers , who report their work in Nature , are now exploring ways of further enhancing the coupling of electrons and photons .
“ We can use light to steer a beam of electrons in space and time , ” says Ropers .
“ An increase in the coupling strength @ @ @ @ @ @ @ an electron , and so allow us to measure optical excitations on the level of individual nanoscopic quantum systems .
Doing so with ultrafast temporal resolution would be simply amazing , and may eventually lead to entirely new quantum technologies for nanoscale sensing and microscopy .
”

Individual electrons interacting with an optical whispering gallery mode. Courtesy: Murat Sivis
Visitors to Saint Paul’s in London are often astonished by the cathedral’s whispering gallery, where words spoken in a whisper along the curving wall of the dome can be heard anywhere along that same wall – including the opposite side of the circular walkway, some 33 metres away. This “whispering gallery effect” is possible because sound runs so easily and smoothly around the dome’s circumference, and variations of it occur wherever waves can travel nearly perfectly around a structure.
Researchers at the University of Göttingen in Germany have now exploited the whispering gallery effect to control the beam of an electron microscope using light. As well as being of fundamental importance, they say that the work might lead to novel technologies for nanoscale sensing and microscopy.
Light wave confined to surface of a sphere
In their work, researchers led by Ofer Kfir and Claus Ropers illuminated small glass spheres with laser light that was trapped in an optical whispering-gallery mode, meaning that it was confined to the surface of the sphere by total internal reflection. Analogous to the acoustic example, the light wave travels around the sphere’s perimeter almost without damping.
The researchers then passed a beam of electrons in a transmission electron microscope near the edge of a sphere. When they measured the distribution of electron velocities using the microscope, they discovered that the electrons had exchanged large amounts of energy with the electric field of the laser light – roughly 10 times more energy, in fact, than any such exchange previously measured in an electron microscope.
The strength of the electron-light interaction comes from two contributions, Kfir explains. First, the whispering-gallery optical modes make it possible to store light and so build up a stronger wave. Second, the velocity of the light wave on the glass sphere matches that of the electron, running at 70% of the speed of light. This matching changes the quantum state of the electron (see image).
The coupling that occurs between an electron and the light’s electric field can be thought of as the acceleration (or deceleration) of the electron by the light field, he tells Physics World. “In the same way a surfer matches the speed of an ocean wave to best use its energy, an electron ‘riding’ the light wave is therefore either purely accelerated or purely decelerated over a substantial distance,” he says. “Indeed, in our study, we observed that individual electrons had picked up or given away the energy of hundreds of photons.”
Further enhancing electron-phonon coupling
As well as being of fundamental interest, the researchers say their findings could bring a greater functionality to electron microscopy – an indispensable characterization tool for research in many scientific disciplines as well as in industry. In Kfir’s view, using light to control the electrons’ quantum state in transmission electron microscopes would open up a range of novel imaging and spectroscopy techniques, making it possible to inspect the optical properties of materials with resolutions down to the atomic scale.
The researchers, who report their work in Nature, are now exploring ways of further enhancing the coupling of electrons and photons. “We can use light to steer a beam of electrons in space and time,” says Ropers. “An increase in the coupling strength would allow a single photon to affect an electron, and so allow us to measure optical excitations on the level of individual nanoscopic quantum systems. Doing so with ultrafast temporal resolution would be simply amazing, and may eventually lead to entirely new quantum technologies for nanoscale sensing and microscopy.”


physicsworld--2020-08-12--White papers: Mad City Labs and SAES Group - Physics World

The content highlighted in this article has been created and hosted by Physics World ’ s corporate partners .
It is free to read but you will be asked to share your contact details with the relevant partner first before being granted access immediately afterwards .
This time we are featuring white papers from Mad City Labs and SAES Group .
Atomic force microscopes ( AFMs ) are versatile tools for characterizing surfaces down to the subnanometre scale .
Researchers wanting to , say , map out the optical antennas they ’ ve inscribed on a chip , or measure @ @ @ @ @ @ @ , can image objects at resolutions down to the picometre level by scanning an AFM over the surface .
Useful as they are , AFMs aren ’ t cheap – typically running at $ 250,000 – which means that they can seem out of reach to many academic scientists , graduate students and researchers at small companies because of their high cost .
Fortunately , researchers can build their own AFMs for as little as $ 30,000 using off-the-shelf components such as nanopositioning stages .
In the Building a Do-it-Yourself Atomic Force Microscope @ @ @ @ @ @ @ the company ’ s director of product development James MacKay describes how home-made AFMs can are not just cheap but high-performance too .
DIY AFMs allow the researchers to customize the design so that they can do whatever kind of surface testing fits their needs and to tune the performance to suit their requirements .
Vacuum engineers and scientists have long known that even if a sample is clean and handled with ultra-high vacuum ( UHV ) standards , a layer of unwanted carbon will form on the material ’ s surface after @ @ @ @ @ @ @ ( HV ) or UHV chamber .
This also happens for materials in the optics vacuum chambers in particle accelerators and synchrotron X-ray beamlines .
Indeed , X-rays can increase the pressure and yield of carbon contaminants by one to two orders of magnitude , significantly reducing how many X-rays end up downstream at experimental stations .
And with next-generation synchrotrons ushering in X-ray brightness increases of two to three orders of magnitude , it is critical to minimize these losses from carbon contamination .
Carbon contamination used to be a show stopper @ @ @ @ @ @ @ cleaned and sometimes even replaced .
But as staff from SAES Group explain in their new white paper ZAO® Based Non Evaporable Getter Pumps in Optics Vacuum Chambers , the company ’ s NEXTorr and CapaciTorr pumps can significantly lower the gases that make the carbon residues form in the first place .
SAES says that its pumps are much smaller and less invasive than traditional varieties , reducing particle-generation to levels acceptable for synchrotron-radiation studies .

The content highlighted in this article has been created and hosted by Physics World’s corporate partners. It is free to read but you will be asked to share your contact details with the relevant partner first before being granted access immediately afterwards.
Welcome to the latest in a new series of sponsored articles showcasing some of the latest white papers and webinars from physics-based businesses around the world
Innovation in action: (left to right) Mad City Labs lets you make a customized atomic force microscope; NEXTorr and CapaciTorr pumps from SAES Group (Courtesy: Mad City Labs and SAES Group).
This time we are featuring white papers from Mad City Labs and SAES Group.
When AFM becomes DIY
Atomic force microscopes (AFMs) are versatile tools for characterizing surfaces down to the subnanometre scale. Researchers wanting to, say, map out the optical antennas they’ve inscribed on a chip, or measure the quantum dots they’ve created, can image objects at resolutions down to the picometre level by scanning an AFM over the surface.
Useful as they are, AFMs aren’t cheap – typically running at $250,000 – which means that they can seem out of reach to many academic scientists, graduate students and researchers at small companies because of their high cost. Fortunately, researchers can build their own AFMs for as little as $30,000 using off-the-shelf components such as nanopositioning stages.
In the Building a Do-it-Yourself Atomic Force Microscope white paper from Mad City Labs, the company’s director of product development James MacKay describes how home-made AFMs can are not just cheap but high-performance too. DIY AFMs allow the researchers to customize the design so that they can do whatever kind of surface testing fits their needs and to tune the performance to suit their requirements.
Cutting carbon contamination
Vacuum engineers and scientists have long known that even if a sample is clean and handled with ultra-high vacuum (UHV) standards, a layer of unwanted carbon will form on the material’s surface after it’s placed in a high-vacuum (HV) or UHV chamber. This also happens for materials in the optics vacuum chambers in particle accelerators and synchrotron X-ray beamlines.
Indeed, X-rays can increase the pressure and yield of carbon contaminants by one to two orders of magnitude, significantly reducing how many X-rays end up downstream at experimental stations. And with next-generation synchrotrons ushering in X-ray brightness increases of two to three orders of magnitude, it is critical to minimize these losses from carbon contamination.
Carbon contamination used to be a show stopper, forcing mirrors to be removed, cleaned and sometimes even replaced. But as staff from SAES Group explain in their new white paper ZAO® Based Non Evaporable Getter Pumps in Optics Vacuum Chambers, the company’s NEXTorr and CapaciTorr pumps can significantly lower the gases that make the carbon residues form in the first place. SAES says that its pumps are much smaller and less invasive than traditional varieties, reducing particle-generation to levels acceptable for synchrotron-radiation studies.


physicsworld--2020-08-13--End-to-end motion QA in radiation therapy treatment planning - Physics World

With the advancement of treatment techniques designed to escalate delivered tumour doses , there is an increasing need for quality-assurance @ @ @ @ @ planning .
Medical physicists are looking to improve treatment delivery by optimizing current 4D IGRT @ @ @ @ @ adaptive techniques .
Modus Medical Devices specializes in end-to-end QA solutions for 4D IGRT .
@ @ @ @ @ overview of our CT and MR-safe motion phantoms with an emphasis on how they will @ @ @ @ @ QA needs .
The webinar , presented by Rocco Flores , will discuss : • @ @ @ @ @ solutions for CT and MR end- to-end motion management .
Rocco Flores is a MRT @ @ @ @ @ specialist .
He has worked at several clinics over 20+ years as a medical radiation @ @ @ @ @ treatment delivery , planning and research .
Since joining Modus QA in 2019 , Rocco @ @ @ @ @ application support and new product development .

Available to watch now, Modus QA explores an overview of our CT and MR-safe motion phantoms
Want to learn more on this subject? Watch now
With the advancement of treatment techniques designed to escalate delivered tumour doses, there is an increasing need for quality-assurance tools in radiation therapy treatment planning. Medical physicists are looking to improve treatment delivery by optimizing current 4D IGRT protocols and exploring rapidly advancing adaptive techniques.
Modus Medical Devices specializes in end-to-end QA solutions for 4D IGRT. This presentation will provide an overview of our CT and MR-safe motion phantoms with an emphasis on how they will meet your current and future QA needs.
The webinar, presented by Rocco Flores, will discuss:
4D IGRT: current and upcoming methods of mitigating patient motion.
The review of Modus QA solutions for CT and MR end- to-end motion management.
Want to learn more on this subject? Watch now
Rocco Flores is a MRT(T) clinical application specialist. He has worked at several clinics over 20+ years as a medical radiation therapist with a focus on treatment delivery, planning and research. Since joining Modus QA in 2019, Rocco is primarily involved in customer application support and new product development.


physicsworld--2020-08-13--Sidestepping the side effects of neurostimulation - Physics World

Stimulation of the vagus nerve by implanted electrodes is used to treat a range of conditions including epilepsy , depression and heart failure .
Such stimulation can also inadvertently activate muscles in the throat , however , leading to treatment-limiting side effects such as pain , difficulty swallowing and shortness of breath .
By measuring nerve and muscle activity in pigs undergoing vagus nerve stimulation ( VNS ) , researchers in the US have identified the mechanism by which the technique causes these side effects .
This new understanding should help clinicians administer VNS at a high enough intensity to @ @ @ @ @ @ @ threshold at which intolerable side effects are triggered .
Despite the effectiveness of VNS at treating some conditions , many details of the process remain unclear .
One of the open questions has to do with the technique ’ s side effects , which recent studies have shown are more severe than researchers would expect .
This can be a problem when those side effects become intolerable at a stimulation level below that at which the technique starts to yield benefits .
The persistence of the mystery around the side effects of VNS @ @ @ @ @ @ @ paucity of human data obtained in the two decades since the technique was first demonstrated .
“ Many of the studies that were used to support the application of VNS in humans were performed in animal models that do not represent human physiology very well , ” says Evan Nicolai , a graduate student at the University of Wisconsin-Madison and the Mayo Clinic .
Writing in the Journal of Neural Engineering , Nicolai and collaborators report how they sought to fill this gap with a series of experiments on pigs , which represent @ @ @ @ @ @ @ The team wrapped either the right or left vagus nerve of 12 anaesthetized animals with a helical electrode cuff of the type used to administer VNS clinically .
They also implanted electrodes to obtain electroneurograms ( ENGs ) from the vagus nerve and electromyograms ( EMGs ) from the cricoarytenoid and cricothyroid muscles .
These muscles , which govern the motion of the larynx , are controlled by impulses from two bundles of nerve fibres that branch off from the vagus trunk : the recurrent laryngeal branch ( RLB ) activates the cricoarytenoid @ @ @ @ @ @ @ SLB ) activates both the cricothyroid and cricoarytenoid muscles .
Nicolai and his colleagues applied a stimulation pulse via the electrode cuff , and measured the timing of the resulting ENG and EMG signals recorded in the vagus nerve and the cricoarytenoid and cricothyroid muscles .
Any delay between the pulse and a muscle ’ s response would indicate that the muscle was activated by a signal following a circuitous route , passing first along the vagus trunk , and then into the motor nerve fibres that branch off .
A prompt response @ @ @ @ @ @ @ indicate that the muscle was activated directly by leakage current taking a shortcut from the nearby electrode cuff .
The researchers found that low levels of stimulation ( around 0.3 mA ) activated the cricoarytenoid muscle with a relatively long latency of 6–10 ms. Pulses of this intensity are well below the tolerable threshold for humans , indicating that signals induced in the RLB are not the cause of the treatment-limiting side effects .
Higher stimulation levels ( around 1.4 mA ) provoked a response in the cricothyroid muscle with a latency of @ @ @ @ @ @ @ pulse strength corresponds approximately to the tolerable limit for clinical VNS .
The researchers conclude , therefore , that the most severe side effects can be attributed to stimulation pulses that are strong enough to activate the nearby SLB directly via leakage currents from the electrode cuff .
The effect of this leakage-induced activation of the SLB could be minimized by using cuff designs with thicker insulation , or by rerouting the nearby nerve branches during surgery .
But the team also has plans for avoiding muscle activation via the fibres that take @ @ @ @ @ @ @ to the RLB .
“ One member of our team , Megan Settell , is leading a project to understand the distribution and orientation of the nerve fibres that make up the vagus , to enable targeting of different fibres before a patient has surgery for VNS , ” says Nicolai .
“ In parallel , our collaborators Warren Grill and Nicole Pelot seek to predict activation of certain nerve fibres in the vagus using computational modelling .
”

Top: cartoon of the pig vagus nerve showing the routes that the recurrent laryngeal branch (RLB) and the superior laryngeal branch (SLB) take to the cricoarytenoid (CA) and cricothyroid (CT) muscles. Bottom: wiring diagram showing the paths taken by electrical signals in response to VNS. (Courtesy: Evan Nicolai)
Stimulation of the vagus nerve by implanted electrodes is used to treat a range of conditions including epilepsy, depression and heart failure. Such stimulation can also inadvertently activate muscles in the throat, however, leading to treatment-limiting side effects such as pain, difficulty swallowing and shortness of breath. By measuring nerve and muscle activity in pigs undergoing vagus nerve stimulation (VNS), researchers in the US have identified the mechanism by which the technique causes these side effects. This new understanding should help clinicians administer VNS at a high enough intensity to achieve therapeutic benefits while keeping below the threshold at which intolerable side effects are triggered.
Despite the effectiveness of VNS at treating some conditions, many details of the process remain unclear. One of the open questions has to do with the technique’s side effects, which recent studies have shown are more severe than researchers would expect. This can be a problem when those side effects become intolerable at a stimulation level below that at which the technique starts to yield benefits.
The persistence of the mystery around the side effects of VNS can be attributed partly to the relative paucity of human data obtained in the two decades since the technique was first demonstrated.
Evan Nicolai, at the Mayo Clinic Graduate School of Biomedical Sciences, performed the work under the mentorship of Kip Ludwig.
“Many of the studies that were used to support the application of VNS in humans were performed in animal models that do not represent human physiology very well,” says Evan Nicolai, a graduate student at the University of Wisconsin-Madison and the Mayo Clinic.
Writing in the Journal of Neural Engineering, Nicolai and collaborators report how they sought to fill this gap with a series of experiments on pigs, which represent a much more human-like animal model.
The team wrapped either the right or left vagus nerve of 12 anaesthetized animals with a helical electrode cuff of the type used to administer VNS clinically. They also implanted electrodes to obtain electroneurograms (ENGs) from the vagus nerve and electromyograms (EMGs) from the cricoarytenoid and cricothyroid muscles. These muscles, which govern the motion of the larynx, are controlled by impulses from two bundles of nerve fibres that branch off from the vagus trunk: the recurrent laryngeal branch (RLB) activates the cricoarytenoid muscle; the superior laryngeal branch (SLB) activates both the cricothyroid and cricoarytenoid muscles.
Nicolai and his colleagues applied a stimulation pulse via the electrode cuff, and measured the timing of the resulting ENG and EMG signals recorded in the vagus nerve and the cricoarytenoid and cricothyroid muscles. Any delay between the pulse and a muscle’s response would indicate that the muscle was activated by a signal following a circuitous route, passing first along the vagus trunk, and then into the motor nerve fibres that branch off. A prompt response, on the other hand, would indicate that the muscle was activated directly by leakage current taking a shortcut from the nearby electrode cuff.
The researchers found that low levels of stimulation (around 0.3 mA) activated the cricoarytenoid muscle with a relatively long latency of 6–10 ms. Pulses of this intensity are well below the tolerable threshold for humans, indicating that signals induced in the RLB are not the cause of the treatment-limiting side effects. Higher stimulation levels (around 1.4 mA) provoked a response in the cricothyroid muscle with a latency of between 4 and 6 ms. This pulse strength corresponds approximately to the tolerable limit for clinical VNS. The researchers conclude, therefore, that the most severe side effects can be attributed to stimulation pulses that are strong enough to activate the nearby SLB directly via leakage currents from the electrode cuff.
The effect of this leakage-induced activation of the SLB could be minimized by using cuff designs with thicker insulation, or by rerouting the nearby nerve branches during surgery. But the team also has plans for avoiding muscle activation via the fibres that take the long way from the stimulation electrode to the RLB.
“One member of our team, Megan Settell, is leading a project to understand the distribution and orientation of the nerve fibres that make up the vagus, to enable targeting of different fibres before a patient has surgery for VNS,” says Nicolai. “In parallel, our collaborators Warren Grill and Nicole Pelot seek to predict activation of certain nerve fibres in the vagus using computational modelling.”


physicsworld--2020-08-13--The funny and sinister sides of machine learning, how to make nanoparticles by the tonne - Physics W

The funny and sinister sides of machine learning, how to make nanoparticles by the tonne - Physics World

Would you use a pick-up line composed by a machine-learning algorithm ?
Perhaps something like You Look Like a Thing and I Love You , which is a machine ’ s attempt at an amorous icebreaker and the title of a book by Janelle Shane .
Shane is an optical engineer with a blog that chronicles the absurdities that are sometimes generated by artificial intelligence ( AI ) systems – and is interviewed in this episode by Physics World ’ s Margaret Harris .
While pick-up lines and recipes generated by AI can be hilarious , Shane cautions that there @ @ @ @ @ @ @ because it can become very good at mimicking human prejudices .
Have you ever wondered how large quantities of nanoparticles can be manufactured to very high precision ?
Ed Lester , founder of UK-based Promethean Particles , explains how the firm ’ s continuous-flow hydrothermal synthesis process does the job using a much more sophisticated version of a method familiar to anyone who grew a “ crystal garden ” in science class .
Lester spun the company out of the University of Nottingham , where he developed the technology .
He looks back @ @ @ @ @ @ @ the process and talks about some exciting new nanoparticle applications such as anti-icing coatings for aeroplanes and artificial bone for medical applications .

Would you use a pick-up line composed by a machine-learning algorithm? Perhaps something like You Look Like a Thing and I Love You, which is a machine’s attempt at an amorous icebreaker and the title of a book by Janelle Shane.
Shane is an optical engineer with a blog that chronicles the absurdities that are sometimes generated by artificial intelligence (AI) systems – and is interviewed in this episode by Physics World’s Margaret Harris. While pick-up lines and recipes generated by AI can be hilarious, Shane cautions that there is also a sinister side to AI because it can become very good at mimicking human prejudices.
Have you ever wondered how large quantities of nanoparticles can be manufactured to very high precision? Ed Lester, founder of UK-based Promethean Particles, explains how the firm’s continuous-flow hydrothermal synthesis process does the job using a much more sophisticated version of a method familiar to anyone who grew a “crystal garden” in science class.
Lester spun the company out of the University of Nottingham, where he developed the technology. He looks back at the challenges of developing and commercializing the process and talks about some exciting new nanoparticle applications such as anti-icing coatings for aeroplanes and artificial bone for medical applications.


physicsworld--2020-08-13--Artificial spider web gets an ionic boost - Physics World

An artificial material with the same elastic , adhesive , self-cleaning , sensing and tensile properties as natural spider silk has been created by researchers in South Korea .
The synthetic web , which is made from a semi-solid stretchy gel , works using electrostatics and might have applications in artificial muscles , grippers and self-cleaning wall-climbing devices .
Spider silk has a tensile strength five times higher than that of steel , and its stretchable threads boast an adhesive coating that enables spiders to capture and trap prey in their webs .
This adhesive coating does have a down @ @ @ @ @ @ @ it attracts contaminants from the environment , causing the webs ’ capturing efficiency to deteriorate .
To overcome this problem , spiders have evolved several strategies for reducing and eliminating dirt and debris from their webs .
One such strategy is to build a minimalist web structure and then wait for prey to fly or crawl into it .
As its prey struggles with the sticky threads , the spider senses the web vibrating , springs into action and wraps its as-yet weakly-bound prey with additional threads .
This traps the prey once @ @ @ @ @ @ @ for a high-surface-area web to which contaminants could more easily adhere .
Another strategy is for the spiders to pull on their webs and then rapidly release them , causing contaminants to bounce off in a catapult-like fashion as the webs vibrate .
Scientists have long been fascinated by spider biology , and many have attempted to mimic either the spiders ’ actuation and sensing or the structural , self-cleaning properties of their silk .
Reproducing the behaviour of spider webs in the laboratory is no simple task , however , and previous @ @ @ @ @ @ @ on recreating the way in which a spider spins its natural web .
A team led by Jeong-Yun Sun and Ho-Young Kim of Seoul National University has now taken a different approach .
Their method involves applying static electricity to fibre-like strands of an ionically conducting and stretchable organogel , which is a semi-solid material made of gelling molecules in an organic solvent ( in this case , covalently cross-liked polyacrylamide chains in ethylene glycol with dissolved lithium chloride ) .
The strands of this organogel are then encapsulated with silicone rubber and @ @ @ @ @ @ @ reduce their surface energy ( and thus surface tension ) .
The researchers , who report their work in Science Robotics , wove these composite fibres into structures that resemble natural spider webs .
They found they could make the web strands electro-adhere to target objects made from metals , ceramics and polymers , thanks to the static electric field that arises between adjacent web strands when a high voltage is applied .
Sun , Kim and colleagues found that these target objects generate an electrical response in the ionic conducting fibres as @ @ @ @ @ @ @ initiating the adhesion process by electrostatics .
They also discovered that they could make the fibres vibrate by applying an electric field between strand pairs .
These vibrations , combined with the fibres ’ hydrophobic coating , help to eliminate contaminants that would otherwise reduce adhesion forces .
Indeed , after self-cleaning , the artificial webs recovered nearly 99 % of their original adhesive force .
In a related article , Jonathan Rossiter , a roboticist at the University of Bristol , UK , and the head of the Soft Robotics group at @ @ @ @ @ @ @ flexible and stretchable ionic conducting materials could be used as substitutes for conventional conductors in future electroactive artificial muscles .
Rossiter , who was not involved in the Seoul team ’ s work , suggests that such structures could come in handy when developing soft robotic wearable assistive devices for older people or people with disabilities .
The study ’ s lead author , Younghoon Lee , agrees , adding that the team ’ s approach could also apply to “ existing robotics components based on electrostatics , such as electrostatic grippers , @ @ @ @ @ @ @ ” .
In addition , the materials ’ ability to self-clean could be exploited in robots that use electro-adhesion to climb walls , and are currently limited to clean , dust-free surfaces .
As a suggestion for future work , Rossiter notes that it would be “ extremely interesting to develop the spider analogy further , potentially seeing how spiders could work with the ionic spider webs in their natural environments , providing new insights into biology.
” For their part , the Seoul team aim to improve the robustness of their web @ @ @ @ @ @ @ them so that they can detect non-charged objects , too .

The artificial ionic spiderweb. Credit: Lee et al., Sci. Robot. 5, eaaz5405 (2020)
An artificial material with the same elastic, adhesive, self-cleaning, sensing and tensile properties as natural spider silk has been created by researchers in South Korea. The synthetic web, which is made from a semi-solid stretchy gel, works using electrostatics and might have applications in artificial muscles, grippers and self-cleaning wall-climbing devices.
Spider silk has a tensile strength five times higher than that of steel, and its stretchable threads boast an adhesive coating that enables spiders to capture and trap prey in their webs. This adhesive coating does have a down side, however, which is that it attracts contaminants from the environment, causing the webs’ capturing efficiency to deteriorate.
To overcome this problem, spiders have evolved several strategies for reducing and eliminating dirt and debris from their webs. One such strategy is to build a minimalist web structure and then wait for prey to fly or crawl into it. As its prey struggles with the sticky threads, the spider senses the web vibrating, springs into action and wraps its as-yet weakly-bound prey with additional threads. This traps the prey once and for all, without the need for a high-surface-area web to which contaminants could more easily adhere. Another strategy is for the spiders to pull on their webs and then rapidly release them, causing contaminants to bounce off in a catapult-like fashion as the webs vibrate.
Mimicking spider actuation and sensing
Scientists have long been fascinated by spider biology, and many have attempted to mimic either the spiders’ actuation and sensing or the structural, self-cleaning properties of their silk. Reproducing the behaviour of spider webs in the laboratory is no simple task, however, and previous attempts to do so have mainly focused on recreating the way in which a spider spins its natural web.
A team led by Jeong-Yun Sun and Ho-Young Kim of Seoul National University has now taken a different approach. Their method involves applying static electricity to fibre-like strands of an ionically conducting and stretchable organogel, which is a semi-solid material made of gelling molecules in an organic solvent (in this case, covalently cross-liked polyacrylamide chains in ethylene glycol with dissolved lithium chloride). The strands of this organogel are then encapsulated with silicone rubber and coated with a hydrophobic perfluorinated compound to reduce their surface energy (and thus surface tension).
The researchers, who report their work in Science Robotics, wove these composite fibres into structures that resemble natural spider webs. They found they could make the web strands electro-adhere to target objects made from metals, ceramics and polymers, thanks to the static electric field that arises between adjacent web strands when a high voltage is applied.
Vibrations help eliminate contaminants
Sun, Kim and colleagues found that these target objects generate an electrical response in the ionic conducting fibres as soon as the fibre touches them, initiating the adhesion process by electrostatics. They also discovered that they could make the fibres vibrate by applying an electric field between strand pairs. These vibrations, combined with the fibres’ hydrophobic coating, help to eliminate contaminants that would otherwise reduce adhesion forces. Indeed, after self-cleaning, the artificial webs recovered nearly 99% of their original adhesive force.
In a related article, Jonathan Rossiter, a roboticist at the University of Bristol, UK, and the head of the Soft Robotics group at the Bristol Robotics Laboratory, notes that flexible and stretchable ionic conducting materials could be used as substitutes for conventional conductors in future electroactive artificial muscles. Rossiter, who was not involved in the Seoul team’s work, suggests that such structures could come in handy when developing soft robotic wearable assistive devices for older people or people with disabilities.
The study’s lead author, Younghoon Lee, agrees, adding that the team’s approach could also apply to “existing robotics components based on electrostatics, such as electrostatic grippers, dielectric elastomer actuators and capacitive tactile sensors”. In addition, the materials’ ability to self-clean could be exploited in robots that use electro-adhesion to climb walls, and are currently limited to clean, dust-free surfaces.
As a suggestion for future work, Rossiter notes that it would be “extremely interesting to develop the spider analogy further, potentially seeing how spiders could work with the ionic spider webs in their natural environments, providing new insights into biology.” For their part, the Seoul team aim to improve the robustness of their web fibres and may also seek to adapt them so that they can detect non-charged objects, too.


physicsworld--2020-08-14--New mechanism could reduce plasma turbulence in stellarators - Physics World

A new mechanism that could reduce plasma turbulence in stellarators has been identified in computer simulations done by researchers in the US and Germany .
A similar effect has already been predicted to occur in tokamaks , which like stellarators , confine hot plasmas using magnetic fields .
A plasma is an extremely hot state of matter in which electrons and ions are no longer bound together .
The Sun is a dense plasma where nuclei have enough energy to undergo fusion , unleashing huge amounts of energy .
Physicists have long dreamed of achieving controlled fusion on Earth because @ @ @ @ @ @ @ energy .
Stellarators are promising candidates for fusion reactors because they could potentially maintain plasmas for up to 30 min , while tokamaks work in a pulsed regime ( 10 s pulses on the ASDEX Upgrade tokamak in Garching , Germany ) .
However , turbulent transport – which causes the loss of both plasma particles and energy – can be an obstacle to maintaining confinement .
In 2018 , Alessandro Di Siena and his co-workers at the Max Plank Institute for Plasma Physics in Garching discovered a new turbulence-stabilizing effect for tokamaks @ @ @ @ @ @ @ The effect involves a resonant interaction between suprathermal ( fast ) ions – generated via ion-cyclotron-resonance-frequency ( ICRF ) heating – and turbulence-driving micro-instabilities .
For this resonance to occur , according to the analytic model they derived , the frequency of the most unstable , turbulence-driving mode must match the drift frequency of the energetic particles , imposing a constraint over the fast ions ’ temperature .
At the same time , whether this effect is stabilizing or destabilizing on the turbulence depends on the relative magnitude of temperature and density gradients @ @ @ @ @ @ @ the latter ) .
Di Siena is now at the University of Texas at Austin and has done this recent stellerator work with team members Alejandro Bañón Navarro , and Frank Jenko in Garching .
They performed nonlinear gyrokinetic simulations to study how this mechanism can be used to stabilize the Wendelstein 7-X ( W7-X ) stellerator at the Max Plank Institute for Plasma Physics in Greifswald .
While W7-X does not have an ICRF heating source yet , these latest predictions may help guide the design of the ICRF antenna at the @ @ @ @ @ @ @ about these results , and we hope they will help in the design and construction of the ICRF heating system in W7-X , ” says Di Siena .
“ According to our predictions , this resonance mechanism might lead to new advanced scenarios with improved plasma confinement .
The next step would be to confirm our findings in stellarator experiments ” .
The simulations reveal that , in a plasma with a similar gradients and frequency matching , a dependency exists between turbulence stabilization and the temperature of the fast ions .
Therefore @ @ @ @ @ @ @ , turbulent transport reaches a plateau at lower turbulence levels .
This behaviour is dissimilar from what they had previously reported for tokamaks , where a minimum value could be reached at a specific fast-ion temperature .
The distinction derives from differences in the intrinsic designs of the two devices : the tokamak ’ s magnetic configuration is axisymmetric and can be described at each position via a single magnetic field line .
In contrast , the stellarator ’ s magnetic geometry is more complex and must be defined by multiple field lines @ @ @ @ @ @ @ each magnetic field line , there is different temperature where turbulence is minimized , explaining the plateau as the combination of all the field line dependencies .
The complicate geometry of stellarator magnets allows researchers to explore many artificial magnetic configurations that could maximize this stabilizing effect .
The researchers looked at hundreds of possible geometries for the most unstable field line and described an optimized condition where the turbulent transport could be minimized .
“ This work is certainly theoretically interesting , and could be experimentally relevant in plasmas in which a @ @ @ @ @ @ @ in fast ions , ” says Per Helander , head of the Stellarator Theory Department in Greifswald .
“ Under these conditions , one could experimentally test this theoretical insight , and such a test would shed valuable light on our understanding of turbulence in fusion plasmas .
Whether the effect is actually important in the burning plasma of a fusion power plant is another question , and will depend on the operational regime.
” The research is described in a paper that has been accepted for publication in Physical Review Letters .

Recreating the Sun: the Wendelstein 7-X stellarator (Courtesy: Gwurden/CC BY-SA 4.0)
A new mechanism that could reduce plasma turbulence in stellarators has been identified in computer simulations done by researchers in the US and Germany. A similar effect has already been predicted to occur in tokamaks, which like stellarators, confine hot plasmas using magnetic fields.
A plasma is an extremely hot state of matter in which electrons and ions are no longer bound together. The Sun is a dense plasma where nuclei have enough energy to undergo fusion, unleashing huge amounts of energy. Physicists have long dreamed of achieving controlled fusion on Earth because it would be a source of clean energy.
Stellarators are promising candidates for fusion reactors because they could potentially maintain plasmas for up to 30 min, while tokamaks work in a pulsed regime (10 s pulses on the ASDEX Upgrade tokamak in Garching, Germany). However, turbulent transport – which causes the loss of both plasma particles and energy – can be an obstacle to maintaining confinement.
Turbulence-stabilizing effect
In 2018, Alessandro Di Siena and his co-workers at the Max Plank Institute for Plasma Physics in Garching discovered a new turbulence-stabilizing effect for tokamaks by doing computer simulations of plasmas. The effect involves a resonant interaction between suprathermal (fast) ions – generated via ion-cyclotron-resonance-frequency (ICRF) heating – and turbulence-driving micro-instabilities. For this resonance to occur, according to the analytic model they derived, the frequency of the most unstable, turbulence-driving mode must match the drift frequency of the energetic particles, imposing a constraint over the fast ions’ temperature. At the same time, whether this effect is stabilizing or destabilizing on the turbulence depends on the relative magnitude of temperature and density gradients (the first must be higher than the latter).
Di Siena is now at the University of Texas at Austin and has done this recent stellerator work with team members Alejandro Bañón Navarro, and Frank Jenko in Garching. They performed nonlinear gyrokinetic simulations to study how this mechanism can be used to stabilize the Wendelstein 7-X (W7-X) stellerator at the Max Plank Institute for Plasma Physics in Greifswald. While W7-X does not have an ICRF heating source yet, these latest predictions may help guide the design of the ICRF antenna at the facility.
Exciting results
“We are very excited about these results, and we hope they will help in the design and construction of the ICRF heating system in W7-X,” says Di Siena. “According to our predictions, this resonance mechanism might lead to new advanced scenarios with improved plasma confinement. The next step would be to confirm our findings in stellarator experiments”.
The simulations reveal that, in a plasma with a similar gradients and frequency matching, a dependency exists between turbulence stabilization and the temperature of the fast ions. Therefore, at a given value of temperature, turbulent transport reaches a plateau at lower turbulence levels. This behaviour is dissimilar from what they had previously reported for tokamaks, where a minimum value could be reached at a specific fast-ion temperature.
The distinction derives from differences in the intrinsic designs of the two devices: the tokamak’s magnetic configuration is axisymmetric and can be described at each position via a single magnetic field line. In contrast, the stellarator’s magnetic geometry is more complex and must be defined by multiple field lines. This latest work shows that for each magnetic field line, there is different temperature where turbulence is minimized, explaining the plateau as the combination of all the field line dependencies.
The complicate geometry of stellarator magnets allows researchers to explore many artificial magnetic configurations that could maximize this stabilizing effect. The researchers looked at hundreds of possible geometries for the most unstable field line and described an optimized condition where the turbulent transport could be minimized.
“This work is certainly theoretically interesting, and could be experimentally relevant in plasmas in which a substantial fraction of the thermal energy resides in fast ions,” says Per Helander, head of the Stellarator Theory Department in Greifswald. “Under these conditions, one could experimentally test this theoretical insight, and such a test would shed valuable light on our understanding of turbulence in fusion plasmas. Whether the effect is actually important in the burning plasma of a fusion power plant is another question, and will depend on the operational regime.”
The research is described in a paper that has been accepted for publication in Physical Review Letters.


physicsworld--2020-08-14--Scepticism beyond pessimism - Physics World

Most readers of Physics World will be familiar with the works of astronomer Carl Sagan , and the writer and producer Ann Druyan .
The husband and wife duo worked together to write , produce and present the seminal 1980s TV series Cosmos , which was , and still is , one of the most watched and beloved science TV productions ever made .
Despite its broad-ranging coverage of many scientific subjects , Cosmos was successful thanks to the perspective it offered to viewers .
It deftly showed us – the Pale Blue Dot – our place in the universe @ @ @ @ @ @ @ s productions were celebrated for their art as much as they were lauded for science communication .
Following in their footsteps , daughter Sasha Sagan has now penned her first book , For Small Creatures Such As We : Rituals and Reflections for Finding Wonder , in which she attempts to unravel the meaning of life , via the many rituals that we attach to big moments of change in our lives .
Where her parents looked to the stars for inspiration , Sasha Sagan ’ s gaze is more squarely on the @ @ @ @ @ @ @ secular world-view learn from the rituals mainly practised by those of the different faiths around the world ?
Sagan , who was herself raised in a secular home , finds that science is at the root of many ritual celebrations in cultures across the globe .
For Small Creatures Such As We explores these rituals and practices we humans punctuate our lives with .
From major life events such as births , marriages and deaths , to the more mundane such as eating , sex and atonement ( those two are not necessarily @ @ @ @ @ @ @ someone with a secular worldview might find the same solace and celebration without the trappings of religion .
Sasha Sagan ’ s love for her parents , and the inspiration she takes from them , is evident throughout , with the title itself drawn from their writing .
Families play a large part in most of life ’ s events , in one way or another , and Sagan ’ s writing turns the lens on her own experience as much as it draws from cultures around the world .
Topics include death @ @ @ @ @ @ @ , plus weekly and monthly rituals .
Sagan ’ s tone is personal and amusing , as she shares stories that are intimate , open and honest .
While she considers many practices from around the world , it is the individual who receives most focus : the personal benefits and pitfalls .
It ’ s clear that the death of her father and the birth of her daughter have played a large part in inspiring Sagan to wonder how people who have no religion might learn from those who do .
Learning @ @ @ @ @ @ @ something but , on occasion , how not to .
There is humour in some of the culturally strange practices , but Sagan writes with neither malice nor judgement .
No worldview is presented as worse or better than another – except where that worldview leads to actual and clear damage to human beings .
Considering the burial rituals of people from Vietnam to Madagascar , from the Amazon to the Great Lakes , Sagan turns her thoughts to the funeral of her father , who died in 1998 aged 62 .
As @ @ @ @ @ @ @ , she tried to shut down her feelings to an extent , to keep the emotions at bay .
Writing about the birth of her daughter , Sagan looks back through the lens that life and research into distant communities has given her .
She wishes she had let herself experience those feelings in full at the time .
It is an emotional passage in a book that , as a whole , deftly navigates weighty topics with humour and a real sense of understanding .
Standing on the shoulders of giants can @ @ @ @ @ @ @ hindrance .
Without skill , you run the risk of filling your work with clichés .
Sagan avoids this adeptly and her writing is imbued with a passion equal to that of her parents .
The book sits somewhere between a memoir and an exploration of social history .
There is anthropology , science and the human experience .
I was left with the feeling that I will turn to it again , for inspiration or reference , and For Small Creatures Such as We now sits on my shelf as a handbook @ @ @ @ @ @ @ The Cosmic Shed , I asked Sagan about her book , and her parents ’ legacy .
What was your inspiration for the book ?
My parents raised me with awe and wonder for the universe as revealed by science .
As a secular home , we had some traditions carried on from our ancestors .
The philosophy was wonderful : it fulfilled some deep philosophical and intellectual needs .
But what it lacks is celebrations , holidays and rites of passage .
I became very interested in that sort of thing .
@ @ @ @ @ @ @ 14 , and the question of how you grieve and mourn without the infrastructure of religion became very central to my life .
I began researching celebrations and rituals and all sorts of ways that human beings mark change and the passage of time .
I found an astonishing thing , which is that much of what we do is the same around the world .
When you peel back the specifics of time and space , when you take away the set design and the script and the elements of theatre , @ @ @ @ @ @ @ changing of the seasons , the equinoxes , solstices , and biological changes like coming of age – these are all scientific events .
My book is an exploration of that , and I try to light-heartedly explore some big questions such as science , religion and death but with a little humour in there .
The book considers “ rituals and reflections for finding wonder ” – tell me a bit more about that In the recent history of human beings , religion and science have veered apart – we have this @ @ @ @ @ @ @ My mother calls it Post-Copernican Stress Disorder .
The rituals and rites of passage and these huge moments in our lives ; the framework for marking them is often religious .
I think that , if you go back far enough , science – in the sense of following the evidence to understand where we are , what we are doing , how things work , how the seasons change , when the crops come , what the animals are doing , what the stars are doing – and the feeling of being @ @ @ @ @ @ @ those things are deeply connected and they can be and should be .
We malign facts as “ cold and hard ” and we have this idea that when we understand something deeply , it takes away the “ magic ” of it .
I think that it is the opposite .
I think that the more deeply we study something and understand it , that ’ s a way of honouring it and celebrating it .
We can all have that excitement about the elements of existence we ’ re curious about @ @ @ @ @ @ @ get this idea that there is beauty and awe and wonder in the way things really are .
It ’ s so powerful .
Change is constant and we live on a planet where nothing stays the same .
There are cyclical changes like the seasons and there are permanent changes like birth and death .
It is really hard to wrap our minds around them , to process them and come to terms with them .
We don ’ t have to look at life through a religious lens to know that @ @ @ @ @ @ @ we need to party !
We need delicious food and to all come together to get through the time when the days are really short .
I think that many of the celebrations that we have created , around the world , are just ways of processing change and whether you believe or not , you still have to process those changes .
One of the biggest changes is the loss of a parent .
A lot of people , even those without a strong faith , might find themselves turning to that @ @ @ @ @ @ @ me about that for you ?
When I lost my dad he had been sick on and off for two years but I just didn ’ t think he was really in mortal peril until the last few days .
Maybe because I was naive , being so young , or I was in denial , or because my mother is a very optimistic and positive person .
I took a really long time to wrap my head around what had happened .
I think if you are brought up with faith and @ @ @ @ @ @ @ be a tendency to think , “ this is what I can go back to in a difficult time ” but because I wasn ’ t really brought up with it I don ’ t think that way .
My family is Jewish : we celebrate Jewish holidays , if I take a DNA test it says “ you are Jewish ” , but not in a theological sense .
In the funeral there were some things that we did for my father , for my grandparents , that fit into the religious @ @ @ @ @ @ @ for how to deal with things in a situation .
But I think that is something different from belief .
Everyone has to navigate those traditions for themselves and I think there ’ s some value in having an idea about what to do when you are really stressed in that moment of grief – where it ’ s almost happening in slow motion and you ’ re not really experiencing it in your true self .
The message that I got from my parents about loss and death was that this does @ @ @ @ @ @ @ we are experiencing right now is very hard and painful , but it does go away .
In fact , in some way that is what makes this moment so special .
There are also other things that are amazing , if you take a step back .
I literally carry on my father , thanks to a secret code in my blood that connects me to him , and all these ancestors I didn ’ t know .
When my daughter was born , he lives on in her too , which @ @ @ @ @ @ @ was presented as this magical thing , instead of just worksheets you get in seventh grade .
My parents wrote a beautiful passage about the written word being a magic trick – a way that someone who has been dead for a thousand years can talk to you inside your head .
These things can seem almost supernatural , but require no faith and they give me a lot of solace .
You ’ ve been a TV producer and are now an author .
That certainly follows in your parents ’ footsteps @ @ @ @ @ @ @ to be missing .
Did you not want to become a scientist ?
I think there may be a word missing from the English language because science is my passion and my worldview .
I think of it like this – not every Catholic is a priest .
It ’ s not my job .
It wasn ’ t my strongest subject in school ; I was much more of a history and literature person .
It is something I read about a lot and it is a source of great inspiration .
@ @ @ @ @ @ @ that means my philosophy is evidence-based and science is the lens through which I see the world .
If someone says “ Do you believe in X , Y or Z ?
” I often say “ My position is I withhold belief without evidence.
” I wish someone would invent a word for that philosophy : “ I ’ m not saying there is not a ghost in your attic .
I ’ m just saying that until I have evidence , I will not say I believe in something.
” Is @ @ @ @ @ @ @ does not have a very friendly connotation .
I want this imaginary word to have a joyful enthusiasm about that which is supported by evidence .
OK.
I ’ m going to call it Saganism .
Well , it ’ s catchy .
I ’ ll give you that .
It sounds a bit like paganism , which is difficult .
Not to mention Satanism [ laughs ] .
I don ’ t want to get mixed up with that .

Physics World. Members of the Institute of Physics can enjoy the full issue Taken from the August 2020 issue of. Members of the Institute of Physics can enjoy the full issue via the Physics World app
Evidence-based enthusiast Sasha Sagan on science, traditions and what makes us human. (Courtesy: Brian C Seitz)
Most readers of Physics World will be familiar with the works of astronomer Carl Sagan, and the writer and producer Ann Druyan. The husband and wife duo worked together to write, produce and present the seminal 1980s TV series Cosmos, which was, and still is, one of the most watched and beloved science TV productions ever made. Despite its broad-ranging coverage of many scientific subjects, Cosmos was successful thanks to the perspective it offered to viewers. It deftly showed us – the Pale Blue Dot – our place in the universe.
Indeed, Sagan and Druyan’s productions were celebrated for their art as much as they were lauded for science communication. Following in their footsteps, daughter Sasha Sagan has now penned her first book, For Small Creatures Such As We: Rituals and Reflections for Finding Wonder, in which she attempts to unravel the meaning of life, via the many rituals that we attach to big moments of change in our lives. Where her parents looked to the stars for inspiration, Sasha Sagan’s gaze is more squarely on the human condition. Can those with a secular world-view learn from the rituals mainly practised by those of the different faiths around the world? Sagan, who was herself raised in a secular home, finds that science is at the root of many ritual celebrations in cultures across the globe.
For Small Creatures Such As We explores these rituals and practices we humans punctuate our lives with. From major life events such as births, marriages and deaths, to the more mundane such as eating, sex and atonement (those two are not necessarily linked), the book considers how someone with a secular worldview might find the same solace and celebration without the trappings of religion. Sasha Sagan’s love for her parents, and the inspiration she takes from them, is evident throughout, with the title itself drawn from their writing. Families play a large part in most of life’s events, in one way or another, and Sagan’s writing turns the lens on her own experience as much as it draws from cultures around the world.
Topics include death, fasting, feasting, the seasons, plus weekly and monthly rituals. Sagan’s tone is personal and amusing, as she shares stories that are intimate, open and honest. While she considers many practices from around the world, it is the individual who receives most focus: the personal benefits and pitfalls. It’s clear that the death of her father and the birth of her daughter have played a large part in inspiring Sagan to wonder how people who have no religion might learn from those who do. Learning is not always about how to do something but, on occasion, how not to. There is humour in some of the culturally strange practices, but Sagan writes with neither malice nor judgement. No worldview is presented as worse or better than another – except where that worldview leads to actual and clear damage to human beings.
Considering the burial rituals of people from Vietnam to Madagascar, from the Amazon to the Great Lakes, Sagan turns her thoughts to the funeral of her father, who died in 1998 aged 62. As a 14-year-old in the middle of grief, she tried to shut down her feelings to an extent, to keep the emotions at bay. Writing about the birth of her daughter, Sagan looks back through the lens that life and research into distant communities has given her. She wishes she had let herself experience those feelings in full at the time. It is an emotional passage in a book that, as a whole, deftly navigates weighty topics with humour and a real sense of understanding.
Standing on the shoulders of giants can be a help as much as a hindrance. Without skill, you run the risk of filling your work with clichés. Sagan avoids this adeptly and her writing is imbued with a passion equal to that of her parents. The book sits somewhere between a memoir and an exploration of social history. There is anthropology, science and the human experience. I was left with the feeling that I will turn to it again, for inspiration or reference, and For Small Creatures Such as We now sits on my shelf as a handbook.
In an interview for my podcast The Cosmic Shed, I asked Sagan about her book, and her parents’ legacy.
What was your inspiration for the book?
My parents raised me with awe and wonder for the universe as revealed by science. As a secular home, we had some traditions carried on from our ancestors. The philosophy was wonderful: it fulfilled some deep philosophical and intellectual needs. But what it lacks is celebrations, holidays and rites of passage. I became very interested in that sort of thing. I lost my dad when I was 14, and the question of how you grieve and mourn without the infrastructure of religion became very central to my life. I began researching celebrations and rituals and all sorts of ways that human beings mark change and the passage of time.
I found an astonishing thing, which is that much of what we do is the same around the world. When you peel back the specifics of time and space, when you take away the set design and the script and the elements of theatre, the actual cause for celebration – the changing of the seasons, the equinoxes, solstices, and biological changes like coming of age – these are all scientific events. My book is an exploration of that, and I try to light-heartedly explore some big questions such as science, religion and death but with a little humour in there.
The book considers “rituals and reflections for finding wonder” – tell me a bit more about that
In the recent history of human beings, religion and science have veered apart – we have this sense that the two are opposed. My mother calls it Post-Copernican Stress Disorder. The rituals and rites of passage and these huge moments in our lives; the framework for marking them is often religious. I think that, if you go back far enough, science – in the sense of following the evidence to understand where we are, what we are doing, how things work, how the seasons change, when the crops come, what the animals are doing, what the stars are doing – and the feeling of being part of something grander than ourselves…I think those things are deeply connected and they can be and should be.
We malign facts as “cold and hard” and we have this idea that when we understand something deeply, it takes away the “magic” of it. I think that it is the opposite. I think that the more deeply we study something and understand it, that’s a way of honouring it and celebrating it. We can all have that excitement about the elements of existence we’re curious about and want to understand, if we get this idea that there is beauty and awe and wonder in the way things really are. It’s so powerful.
Change is constant and we live on a planet where nothing stays the same. There are cyclical changes like the seasons and there are permanent changes like birth and death. It is really hard to wrap our minds around them, to process them and come to terms with them. We don’t have to look at life through a religious lens to know that when it is cold and dark, we need to party! We need delicious food and to all come together to get through the time when the days are really short. I think that many of the celebrations that we have created, around the world, are just ways of processing change and whether you believe or not, you still have to process those changes.
Sasha Sagan with her parents Carl Sagan and Ann Druyan. (Courtesy: Sasha Sagan)
One of the biggest changes is the loss of a parent. A lot of people, even those without a strong faith, might find themselves turning to that faith for solace. Can you tell me about that for you?
When I lost my dad he had been sick on and off for two years but I just didn’t think he was really in mortal peril until the last few days. Maybe because I was naive, being so young, or I was in denial, or because my mother is a very optimistic and positive person. I took a really long time to wrap my head around what had happened. I think if you are brought up with faith and then you leave it, there can be a tendency to think, “this is what I can go back to in a difficult time” but because I wasn’t really brought up with it I don’t think that way.
My family is Jewish: we celebrate Jewish holidays, if I take a DNA test it says “you are Jewish”, but not in a theological sense. In the funeral there were some things that we did for my father, for my grandparents, that fit into the religious framework because it’s a recipe for how to deal with things in a situation. But I think that is something different from belief. Everyone has to navigate those traditions for themselves and I think there’s some value in having an idea about what to do when you are really stressed in that moment of grief – where it’s almost happening in slow motion and you’re not really experiencing it in your true self.
The message that I got from my parents about loss and death was that this does not go on forever – that what we are experiencing right now is very hard and painful, but it does go away. In fact, in some way that is what makes this moment so special. There are also other things that are amazing, if you take a step back. I literally carry on my father, thanks to a secret code in my blood that connects me to him, and all these ancestors I didn’t know. When my daughter was born, he lives on in her too, which is so magical. If only genetics was presented as this magical thing, instead of just worksheets you get in seventh grade. My parents wrote a beautiful passage about the written word being a magic trick – a way that someone who has been dead for a thousand years can talk to you inside your head. These things can seem almost supernatural, but require no faith and they give me a lot of solace.
You’ve been a TV producer and are now an author. That certainly follows in your parents’ footsteps but there is one thing that seems to be missing. Did you not want to become a scientist?
I think there may be a word missing from the English language because science is my passion and my worldview. I think of it like this – not every Catholic is a priest. It’s not my job. It wasn’t my strongest subject in school; I was much more of a history and literature person. It is something I read about a lot and it is a source of great inspiration. But I wish there was a word that means my philosophy is evidence-based and science is the lens through which I see the world. If someone says “Do you believe in X, Y or Z?” I often say “My position is I withhold belief without evidence.” I wish someone would invent a word for that philosophy: “I’m not saying there is not a ghost in your attic. I’m just saying that until I have evidence, I will not say I believe in something.”
Is that not scepticism?
Well, scepticism does not have a very friendly connotation. I want this imaginary word to have a joyful enthusiasm about that which is supported by evidence.
OK. I’m going to call it Saganism.
Well, it’s catchy. I’ll give you that.
It sounds a bit like paganism, which is difficult.
Not to mention Satanism [laughs]. I don’t want to get mixed up with that.
2019 Murdoch Books 288pp £14.99


physicsworld--2020-08-14--Grasshopper jumping on a Bloch sphere, red bricks store electrical energy, dynamics of jail dodgebal

Grasshopper jumping on a Bloch sphere, red bricks store electrical energy, dynamics of jail dodgeball - Physics World

A few years ago , the physicists Olga Goulko , Damián Pitalúa-García and Adrian Kent proposed the grasshopper problem .
Think of a grasshopper that hops a fixed distance in a random direction .
If the grasshopper begins at a random position on a lawn , which shape of lawn has the highest probability of retaining the grasshopper ?
It turns out that the answer is not a circle or other simple shape , but rather a rich variety of different shapes at different jump sizes .
What is more , the work provides useful insight into Bell-type inequalities relating @ @ @ @ @ @ @ separated quantum-entangled particles .
Now , Goulko and Kent have teamed-up with Dmitry Chistikov and Mike Paterson at the University of Warwick to look at the grasshopper problem on a sphere .
Again , they found that a variety of shapes emerged as solutions depending on hopping distance .
A Bloch sphere is a geometrical representation of the state space of a single quantum bit – so , once again the research provided insights into entangled particles .
Humans have been making red bricks for thousands of years , but Julio D ’ @ @ @ @ @ @ @ St. Louis are probably the first to think of using the near-ubiquitous building material to store electrical energy .
By coating the bricks with a conducting polymer , they created a supercapacitor .
To demonstrate their device , they used it to power a LED .
The team suggests that walls of brick supercapacitors could be used to store energy .
The game of jail dodgeball involves players on two teams throwing balls at each other .
When a player is hit , they leave the court of play and move to an @ @ @ @ @ @ @ players can re-join the game if they catch a ball that has been thrown out of play .
A team wins when all their opponents are in jail .
Now , Perrin Ruth and Juan Restrepo of the University of Colorado at Boulder have studied the game as a complex system using several mathematical techniques .
Writing in a preprint on arXiv , they say their analysis reveals a “ rich landscape with different game dynamics occurring depending on the strategies used by the teams , which can in some cases be mapped @ @ @ @ @ @ @ .
Ruth and Restrepo also say that they have used mathematics to “ construct a strategy to increase the probability of winning ” .
I am looking forward to testing this out when our Scout troop can meet again – dodgeball is one of our favourite games .

Hop to it: the grasshopper problem has been solved on a sphere. (Courtesy: Tomfriedel/ CC BY 3.0)
A few years ago, the physicists Olga Goulko, Damián Pitalúa-García and Adrian Kent proposed the grasshopper problem. Think of a grasshopper that hops a fixed distance in a random direction. If the grasshopper begins at a random position on a lawn, which shape of lawn has the highest probability of retaining the grasshopper?
It turns out that the answer is not a circle or other simple shape, but rather a rich variety of different shapes at different jump sizes. What is more, the work provides useful insight into Bell-type inequalities relating probabilities of the spin states of two separated quantum-entangled particles.
Now, Goulko and Kent have teamed-up with Dmitry Chistikov and Mike Paterson at the University of Warwick to look at the grasshopper problem on a sphere. Again, they found that a variety of shapes emerged as solutions depending on hopping distance. A Bloch sphere is a geometrical representation of the state space of a single quantum bit – so, once again the research provided insights into entangled particles.
Polymer coating
Humans have been making red bricks for thousands of years, but Julio D’Arcy and colleagues at Washington University in St. Louis are probably the first to think of using the near-ubiquitous building material to store electrical energy. By coating the bricks with a conducting polymer, they created a supercapacitor. To demonstrate their device, they used it to power a LED. The team suggests that walls of brick supercapacitors could be used to store energy.
The game of jail dodgeball involves players on two teams throwing balls at each other. When a player is hit, they leave the court of play and move to an adjacent “jail” area. Jailed players can re-join the game if they catch a ball that has been thrown out of play. A team wins when all their opponents are in jail.
Now, Perrin Ruth and Juan Restrepo of the University of Colorado at Boulder have studied the game as a complex system using several mathematical techniques. Writing in a preprint on arXiv, they say their analysis reveals a “rich landscape with different game dynamics occurring depending on the strategies used by the teams, which can in some cases be mapped to scenarios in competitive species models”. Ruth and Restrepo also say that they have used mathematics to “construct a strategy to increase the probability of winning”. I am looking forward to testing this out when our Scout troop can meet again – dodgeball is one of our favourite games.