physicsworld--2020-07-27--Researchers form single molecule in an optical tweezer - Physics World

Researchers at Harvard University in the US have used optical tweezers to create a single molecule from a single pair of atoms .
The technique they employed , known as magnetoassociation , made it possible to create the molecule in a specific , reversible , quantum state .
The work is thus an important step towards creating low-entropy samples of molecules for applications in quantum computing and quantum simulation .
In their experiment , researchers led by Kang-Kuen Ni confined a sodium ( Na ) atom and a caesium ( Cs ) atom at the centre of an optical trap @ @ @ @ @ @ @ an intense spot .
They then converted the trapped atoms into a molecule by ramping up the ambient magnetic field .
“ In this process [ magnetoassociation ] , the resulting quantum state of the molecule is entirely determined by the state of the initial atoms , ” explains study lead author Jessie Zhang .
“ By carefully preparing the initial atomic states , we can create the molecule in specific motional and internal states.
” Simply put , this means that if the atoms are all prepared in their lowest motional state @ @ @ @ @ @ @ be in its lowest motional state .
If , on the other hand , the atoms are carefully prepared in an excited motional state , the molecule formed is rotationally excited .
The magnetoassociation method has previously been employed to create molecules in various other cold-atom systems , Zhang says , but these were generally larger ensembles containing more atoms .
While the lifetime of the molecules thus produced was sometimes much longer than in the current work , it proved more difficult to control the molecules individually .
“ Our work builds @ @ @ @ @ @ @ to form single molecules from single pairs of atoms in optical tweezers , ” Zhang tells Physics World .
The new technique also improves on two earlier methods demonstrated by Ni and her team .
In their first study , the researchers used a laser to bind a pair of atoms into an excited molecular state through a process called photoassociation .
In the second , they used a pair of laser beams to convert an atom pair into a weakly-bound molecule .
Both efforts had drawbacks , Zhang says .
“ In @ @ @ @ @ @ @ decayed into a large number of states that we couldn ’ t detect and in the second , the laser beam destroyed the molecule it formed , ” she explains .
In contrast , the molecules created by magnetoassociation live long enough to be dissociated back into atoms in their original states , and subsequently detected .
The molecules formed in the new study , which is detailed in Physical Review Letters , are , as yet , only weakly bound .
Among other implications , the weakness of the bond between the @ @ @ @ @ @ @ possess a large electric dipole moment – a necessary condition for quantum computing applications that require entanglement between the atoms ’ quantum states .
To overcome this problem , Ni and colleagues say they will attempt to bring the molecules into their absolute ground state , where they are more stable and can interact with each other via dipole-dipole interactions .
As well as producing entangled molecules , the team also hope to scale up their technique .
“ At present , we only have one molecule in a single tweezer , but @ @ @ @ @ @ @ multiple tweezers , each holding a single molecule that we can individually control , ” Zhang says .
“ We can then envision using such a system as a quantum computer or quantum simulator .
”

Merging two atoms into a molecule with a precise, reversible quantum state that lives long enough to measure. Courtesy: J. Zhang/Harvard University
Researchers at Harvard University in the US have used optical tweezers to create a single molecule from a single pair of atoms. The technique they employed, known as magnetoassociation, made it possible to create the molecule in a specific, reversible, quantum state. The work is thus an important step towards creating low-entropy samples of molecules for applications in quantum computing and quantum simulation.
In their experiment, researchers led by Kang-Kuen Ni confined a sodium (Na) atom and a caesium (Cs) atom at the centre of an optical trap formed by focusing a laser beam to an intense spot. They then converted the trapped atoms into a molecule by ramping up the ambient magnetic field. “In this process [magnetoassociation], the resulting quantum state of the molecule is entirely determined by the state of the initial atoms,” explains study lead author Jessie Zhang. “By carefully preparing the initial atomic states, we can create the molecule in specific motional and internal states.”
Simply put, this means that if the atoms are all prepared in their lowest motional state, the molecule that forms will also be in its lowest motional state. If, on the other hand, the atoms are carefully prepared in an excited motional state, the molecule formed is rotationally excited.
Improving on earlier methods
The magnetoassociation method has previously been employed to create molecules in various other cold-atom systems, Zhang says, but these were generally larger ensembles containing more atoms. While the lifetime of the molecules thus produced was sometimes much longer than in the current work, it proved more difficult to control the molecules individually. “Our work builds on this previous research and expands it to form single molecules from single pairs of atoms in optical tweezers,” Zhang tells Physics World.
The new technique also improves on two earlier methods demonstrated by Ni and her team. In their first study, the researchers used a laser to bind a pair of atoms into an excited molecular state through a process called photoassociation. In the second, they used a pair of laser beams to convert an atom pair into a weakly-bound molecule. Both efforts had drawbacks, Zhang says. “In the first method, the excited molecule decayed into a large number of states that we couldn’t detect and in the second, the laser beam destroyed the molecule it formed,” she explains. In contrast, the molecules created by magnetoassociation live long enough to be dissociated back into atoms in their original states, and subsequently detected.
Weak bonds
The molecules formed in the new study, which is detailed in Physical Review Letters, are, as yet, only weakly bound. Among other implications, the weakness of the bond between the atoms means that the molecules do not possess a large electric dipole moment – a necessary condition for quantum computing applications that require entanglement between the atoms’ quantum states. To overcome this problem, Ni and colleagues say they will attempt to bring the molecules into their absolute ground state, where they are more stable and can interact with each other via dipole-dipole interactions.
As well as producing entangled molecules, the team also hope to scale up their technique. “At present, we only have one molecule in a single tweezer, but the idea is to scale up to multiple tweezers, each holding a single molecule that we can individually control,” Zhang says. “We can then envision using such a system as a quantum computer or quantum simulator.”


physicsworld--2020-07-24--Earth’s atmosphere rings like a giant bell, say researchers - Physics World

The Earth ’ s entire atmosphere vibrates like a giant bell , with various large-scale resonant waves travelling in both directions around the globe .
That is the conclusion of scientists in Japan and the US , who have confirmed a nearly two-centuries-old hypothesis of atmospheric resonance .
Their research should help improve both weather forecasts and long-term climate forecasts .
The fundamentals of atmospheric resonance were first laid out in the early 1800s by the French scholar and mathematician Pierre-Simon Laplace .
“ Laplace showed that amidst all the complications of the atmospheric dynamics there should be a set @ @ @ @ @ @ @ in the vertical – i.e .
trapped against the earth ’ s surface –and propagating purely in the horizontal , ’ explains atmospheric scientist Kevin Hamilton of the University of Hawaiʻi at Mānoa .
He adds , Laplace predicted “ that the horizontal properties of these waves should be the same as for a uniformly deep ocean covering the whole earth with some ‘ equivalent depth ’ .
” The nature of this horizontal structure is governed by Laplace ’ s tidal equation .
Researchers have been able to readily identify the forced @ @ @ @ @ @ @ Earth – atmospheric thermal tides – also predicted as a result of Laplace ’ s initial work .
However , despite considerable subsequent work , their presence of Laplace ’ s waves had remained undetected .
This is because the waves have both very large horizontal scales and short periods of a day or less , which puts them into an observational gap between studies of small-scale phenomena operating over small timescales ( like individual thunderstorms , for example ) and larger-scale features with periods of a day or more .
In their @ @ @ @ @ @ @ colleague Takatoshi Sakazaki — a physicist from Japan ’ s Kyoto University – have used re-analysis data from the European Centre for Medium Range Weather Forecasts to examine atmospheric pressure across the globe on an hourly basis from 1979–2016 .
The team ’ s examination of surface pressure values from the new data set revealed dozens of the predicted normal wave modes , typically with periods between two and thirty-three hours that travel horizontally around the globe at speeds in excess of 1100 km/h .
The team found that the propagation of these @ @ @ @ @ @ @ high and low pressure that encircles the globe .
“ For these rapidly moving wave modes , our observed frequencies and global patterns match those theoretically predicted very well , ” said Sakazaki .
“ It is exciting to see the vision of Laplace and other pioneering physicists so completely validated after two centuries.
” “ Our identification of so many modes in real data shows that the atmosphere is indeed ringing like a bell , ” agreed Hamilton .
“ This finally resolves a longstanding and classic issue in atmospheric science , @ @ @ @ @ @ @ of research to understand both the processes that excite the waves and those that act to damp the waves.
” According to Hamilton , possible drivers of the resonant waves may include a global effect of far small-scale latent heating in the atmosphere from convection , or excitation through part of the turbulent cascades of energy through the atmosphere .
“ As an analogy , imagine a bathtub full of water .
Take a paddle and vigorously stir for a few seconds .
Wait for a minute and see how the flow develops @ @ @ @ @ @ @ will see small scale motions as a result of the turbulent interactions , but you will also notice a more organized sloshing on the bathtub-wide scale at the natural resonance frequencies.
” With their initial study complete , the researchers are now looking to undertake comparisons between their findings and the outputs of global climate models .
The findings are “ a beautiful example of fundamental theory confirmed in observations – something not very common in a complex system like the Earth ’ s atmosphere , ” comments Ted Shepherd , a climate @ @ @ @ @ @ @ the UK .
“ There have been recent developments advocating for renewed attention to these modes as a diagnostic of atmospheric behaviour , ” he added .
“ This new study shows how surface pressure observations have the potential to unlock that opportunity.
” “ The normal modes detected now could prove useful to test models of Earth ’ s circulation , ” agreed Stephen Lewis , an atmospheric physicist from the UK ’ s Open University .
In addition , he added , the wave modes “ even have connections to modes @ @ @ @ @ @ @ thinner atmosphere of Mars.
” The research is described in the Journal of Atmospheric Sciences .

The big picture: scientists have spotted large-scale resonant waves travelling in both directions around the globe. (Courtesy: NASA)
The Earth’s entire atmosphere vibrates like a giant bell, with various large-scale resonant waves travelling in both directions around the globe. That is the conclusion of scientists in Japan and the US, who have confirmed a nearly two-centuries-old hypothesis of atmospheric resonance. Their research should help improve both weather forecasts and long-term climate forecasts.
The fundamentals of atmospheric resonance were first laid out in the early 1800s by the French scholar and mathematician Pierre-Simon Laplace. “Laplace showed that amidst all the complications of the atmospheric dynamics there should be a set of wave motions with energy content trapped in the vertical – i.e. trapped against the earth’s surface –and propagating purely in the horizontal,’ explains atmospheric scientist Kevin Hamilton of the University of Hawaiʻi at Mānoa.
He adds, Laplace predicted “that the horizontal properties of these waves should be the same as for a uniformly deep ocean covering the whole earth with some ‘equivalent depth’.” The nature of this horizontal structure is governed by Laplace’s tidal equation.
Researchers have been able to readily identify the forced waves associated with the rotation of the Earth – atmospheric thermal tides – also predicted as a result of Laplace’s initial work. However, despite considerable subsequent work, their presence of Laplace’s waves had remained undetected.
Observational gap
This is because the waves have both very large horizontal scales and short periods of a day or less, which puts them into an observational gap between studies of small-scale phenomena operating over small timescales (like individual thunderstorms, for example) and larger-scale features with periods of a day or more.
Vibrational modes: computer simulations showing a pattern of low (blue) and high (red) pressure areas move eastward in the atmosphere through time. The effect is generated by just two of the ringing vibrations of the global atmosphere (periods of 32.4 h and 9.4 h). (Courtesy: Sakazaki and Hamilton (2020))
In their new study, however, Hamilton and colleague Takatoshi Sakazaki — a physicist from Japan’s Kyoto University – have used re-analysis data from the European Centre for Medium Range Weather Forecasts to examine atmospheric pressure across the globe on an hourly basis from 1979–2016. The team’s examination of surface pressure values from the new data set revealed dozens of the predicted normal wave modes, typically with periods between two and thirty-three hours that travel horizontally around the globe at speeds in excess of 1100 km/h. The team found that the propagation of these waves results in a checkerboard-style pattern of high and low pressure that encircles the globe.
“For these rapidly moving wave modes, our observed frequencies and global patterns match those theoretically predicted very well,” said Sakazaki. “It is exciting to see the vision of Laplace and other pioneering physicists so completely validated after two centuries.”
New avenue of research
“Our identification of so many modes in real data shows that the atmosphere is indeed ringing like a bell,” agreed Hamilton. “This finally resolves a longstanding and classic issue in atmospheric science, but it also opens a new avenue of research to understand both the processes that excite the waves and those that act to damp the waves.”
According to Hamilton, possible drivers of the resonant waves may include a global effect of far small-scale latent heating in the atmosphere from convection, or excitation through part of the turbulent cascades of energy through the atmosphere.
“As an analogy, imagine a bathtub full of water. Take a paddle and vigorously stir for a few seconds. Wait for a minute and see how the flow develops,” he explains. “You will see small scale motions as a result of the turbulent interactions, but you will also notice a more organized sloshing on the bathtub-wide scale at the natural resonance frequencies.”
Global climate models
With their initial study complete, the researchers are now looking to undertake comparisons between their findings and the outputs of global climate models.
The findings are “a beautiful example of fundamental theory confirmed in observations – something not very common in a complex system like the Earth’s atmosphere,” comments Ted Shepherd, a climate scientist at the University of Reading in the UK.
“There have been recent developments advocating for renewed attention to these modes as a diagnostic of atmospheric behaviour,” he added. “This new study shows how surface pressure observations have the potential to unlock that opportunity.”
“The normal modes detected now could prove useful to test models of Earth’s circulation,” agreed Stephen Lewis, an atmospheric physicist from the UK’s Open University. In addition, he added, the wave modes “even have connections to modes that could play a role in the thinner atmosphere of Mars.”
The research is described in the Journal of Atmospheric Sciences.


physicsworld--2020-07-24--COVID-19 hits Nobel banquet, Plato was right, incubator noise - Physics World

This year ’ s Nobel laureates will have to forgo the lavish Nobel banquet that is held in December .
The Nobel Foundation , which manages the Nobel prizes that are announced in early October , said this week that the banquet is cancelled due to the ongoing COVID-19 pandemic .
Each year the prize winners are invited to Stockholm for talks , the Nobel ceremony as well as the banquet , which is housed in Stockholm ’ s City Hall .
The winners , together with the Swedish royal family and some 1300 guests , are treated to a @ @ @ @ @ @ @ this year .
“ It is unreasonable to hold these events in 2020 , ” the foundation notes .
This is the first time the banquet has been cancelled since 1956 .
The foundation has said that the award ceremonies will still be held this year , but in “ new forms ” .
The Greek philosopher Plato believed that the universe was made of five types of matter : earth , air , fire , water and the cosmos .
Each was described with a particular geometry and for earth that shape @ @ @ @ @ @ @ that maybe he was onto something .
A team from the US and Hungary measured and analysed fragmentation patterns of rocks that they collected as well as from previously assembled datasets , finding that the resulting shape of the fragments is indeed a cube .
“ It turns out that Plato ’ s conception about the element earth being made up of cubes is , literally , the statistical average model for real Earth , ” says geophysicist Douglas Jerolmack from University of Pennsylvania .
“ And that is just mind-blowing.
” And @ @ @ @ @ @ @ when lying in an incubator ?
According to the World Health Organisation , around 15 million babies are born prematurely each year and given babies ’ inability to regulate their temperature they often need to be placed in an incubator .
Around 2–10 % of babies born prematurely suffer hearing loss .
A reason for this could be the high levels of noise that they are subjected to in an incubator , compared to the filtering and absorption of background noise that happens naturally in the womb .
An interdisciplinary team from the @ @ @ @ @ @ @ sounds inside an incubator , finding that while high and medium frequencies were largely suppressed , low frequencies were instead amplified .
The researchers also discovered that when access doors to the incubator were left open , noise levels shot up , particularly those from devices such as respirators .
“ At a high flow-rate with the associated roaring sound , the increase is such that it equates to the noise of a vacuum cleaner at a distance of one metre ( 75 dB ) , ” the authors write , adding that @ @ @ @ @ @ @ in new , quieter technologies .

Cancelled: the December banquet for this year's Nobel laureates will not go ahead due to the COVID-19 pandemic. (Courtesy: Nobel Media AB 2016/Alexander Mahmoud)
This year’s Nobel laureates will have to forgo the lavish Nobel banquet that is held in December. The Nobel Foundation, which manages the Nobel prizes that are announced in early October, said this week that the banquet is cancelled due to the ongoing COVID-19 pandemic.
Each year the prize winners are invited to Stockholm for talks, the Nobel ceremony as well as the banquet, which is housed in Stockholm’s City Hall. The winners, together with the Swedish royal family and some 1300 guests, are treated to a multi-course dinner and entertainment, but not this year. “It is unreasonable to hold these events in 2020,” the foundation notes.
This is the first time the banquet has been cancelled since 1956. The foundation has said that the award ceremonies will still be held this year, but in “new forms”.
The Greek philosopher Plato believed that the universe was made of five types of matter: earth, air, fire, water and the cosmos. Each was described with a particular geometry and for earth that shape was the cube. New research shows that maybe he was onto something.
A team from the US and Hungary measured and analysed fragmentation patterns of rocks that they collected as well as from previously assembled datasets, finding that the resulting shape of the fragments is indeed a cube. “It turns out that Plato’s conception about the element earth being made up of cubes is, literally, the statistical average model for real Earth,” says geophysicist Douglas Jerolmack from University of Pennsylvania. “And that is just mind-blowing.”
And finally, what do premature babies hear when lying in an incubator? According to the World Health Organisation, around 15 million babies are born prematurely each year and given babies’ inability to regulate their temperature they often need to be placed in an incubator. Around 2–10% of babies born prematurely suffer hearing loss. A reason for this could be the high levels of noise that they are subjected to in an incubator, compared to the filtering and absorption of background noise that happens naturally in the womb.
An interdisciplinary team from the Medical University of Vienna has measured the sounds inside an incubator, finding that while high and medium frequencies were largely suppressed, low frequencies were instead amplified. The researchers also discovered that when access doors to the incubator were left open, noise levels shot up, particularly those from devices such as respirators. “At a high flow-rate with the associated roaring sound, the increase is such that it equates to the noise of a vacuum cleaner at a distance of one metre (75 dB),” the authors write, adding that the results show the need to invest in new, quieter technologies.


physicsworld--2020-07-24--Physicists create quantum phase battery - Physics World

Researchers in Spain and Italy have constructed the first-ever quantum phase battery – a device that maintains a phase difference between two points in a superconducting circuit .
The battery , which consists of an indium arsenide ( InAs ) nanowire in contact with aluminium ( Al ) superconducting leads , could be used in quantum computing circuits .
It might also find applications in magnetometry and highly sensitive detectors based on superconductors .
In a classical battery ( also known as the Volta pile ) , chemical energy is converted into a voltage difference .
The resulting current flow @ @ @ @ @ @ @ circuits .
In quantum circuits and devices based on superconducting materials , however , current may flow without an applied external voltage , thus dispensing with the need for a classical battery .
The concept of a quantum phase battery was studied theoretically in 2015 by Sebastián Bergeret of the Material Physics Center ( CFM-CSIC ) and Ilya Tokatly at the University of the Basque Country in Donostia-San Sebastián , Spain .
Their battery design comprised a combination of superconducting and magnetic materials and was based on a Josephson junction – a non-superconducting @ @ @ @ @ @ @ for superconductivity can tunnel .
This semiconducting “ weak link ” provides a persistent phase difference between the superconductors in the circuit , similar to the way that a classical battery provides a persistent voltage drop in an electronic circuit .
Thanks to this phase difference , a superconducting current ( that is , a current with zero dissipation ) flows when the junction is embedded in the superconducting circuit .
In a follow-up to this work , researchers led by Francesco Giazotto and Elia Strambini at the NEST-CNR Nanoscience Institute in Pisa @ @ @ @ @ @ @ identified a suitable material combination for making such a battery .
Their new device is made of n-doped InAs nanowires , which form its core ( or pile ) , and Al superconducting leads acting as poles .
The surface of the nanowires is “ decorated ” with magnetic moments originating from surface oxide states of the material .
The battery works using the so-called anomalous Josephson effect .
In a normal Josephson junction , a superconducting current flows whenever there is a phase difference between two ends of the junction .
Such @ @ @ @ @ @ @ for example , by placing the junction in a superconducting loop and applying a magnetic field .
In contrast , a phase battery provides such a phase difference without the need for this external magnetic field .
Instead , the difference is induced by a geometrical effect that involves the interplay between three phenomena : superconductivity ; spin-orbit coupling ( which describes the interaction between the intrinsic spin of an electron in a solid and the magnetic field induced by the motion of electron ) ; and a magnetic exchange field ( which @ @ @ @ @ @ @ ordinary magnetic field ) .
“ The choice of material for making such a battery was not a simple matter , ” explains team member Andrea Iorio .
“ In our device , the Al superconducting leads provide the superconductivity , the spin-orbit coupling is an intrinsic property of the InAs nanowire and the magnetic impurities provide the local exchange field.
” While the battery needs to be charged by polarizing the magnetic impurities with an external magnetic field , the researchers say the phase bias between the poles persists even when they @ @ @ @ @ @ @ can control the value of the phase difference either by changing the direction of the polarization of the magnetic impurities or by modifying the length of the semiconducting wires .
Trying out other material combinations The researchers , who report their work in Nature Nanotechnology , say they are now exploring other material combinations to improve the device ’ s performance and their ability to control it , as well as making it easier to integrate into quantum circuits .
“ One idea we are pushing forward is to use a superconducting wire @ @ @ @ @ @ @ a battery , ” Iorio explains .
“ The latter will provide a sizeable exchange field that we can accurately control and we are fabricating and characterizing such a system at the moment.
” The Pisa/San Sebastián research teams are also involved in a European project called SUPERTED that aims to engineer ultrasensitive radiation detectors based on superconductor-ferromagnetic insulator structures , and in particular EuS/Al junctions .
“ Such systems could be adapted to construct phase batteries with better performance , ” Iorio tells Physics World .

The first quantum phase battery. (Courtesy: Andrea Iorio)
Researchers in Spain and Italy have constructed the first-ever quantum phase battery – a device that maintains a phase difference between two points in a superconducting circuit. The battery, which consists of an indium arsenide (InAs) nanowire in contact with aluminium (Al) superconducting leads, could be used in quantum computing circuits. It might also find applications in magnetometry and highly sensitive detectors based on superconductors.
In a classical battery (also known as the Volta pile), chemical energy is converted into a voltage difference. The resulting current flow can then be used to power electronic circuits. In quantum circuits and devices based on superconducting materials, however, current may flow without an applied external voltage, thus dispensing with the need for a classical battery.
Josephson junction-based device
The concept of a quantum phase battery was studied theoretically in 2015 by Sebastián Bergeret of the Material Physics Center (CFM-CSIC) and Ilya Tokatly at the University of the Basque Country in Donostia-San Sebastián, Spain. Their battery design comprised a combination of superconducting and magnetic materials and was based on a Josephson junction – a non-superconducting region through which the Cooper pairs responsible for superconductivity can tunnel. This semiconducting “weak link” provides a persistent phase difference between the superconductors in the circuit, similar to the way that a classical battery provides a persistent voltage drop in an electronic circuit. Thanks to this phase difference, a superconducting current (that is, a current with zero dissipation) flows when the junction is embedded in the superconducting circuit.
In a follow-up to this work, researchers led by Francesco Giazotto and Elia Strambini at the NEST-CNR Nanoscience Institute in Pisa and the University of Salerno have now identified a suitable material combination for making such a battery. Their new device is made of n-doped InAs nanowires, which form its core (or pile), and Al superconducting leads acting as poles. The surface of the nanowires is “decorated” with magnetic moments originating from surface oxide states of the material.
The anomalous Josephson effect
The battery works using the so-called anomalous Josephson effect. In a normal Josephson junction, a superconducting current flows whenever there is a phase difference between two ends of the junction. Such a phase difference can be induced, for example, by placing the junction in a superconducting loop and applying a magnetic field.
In contrast, a phase battery provides such a phase difference without the need for this external magnetic field. Instead, the difference is induced by a geometrical effect that involves the interplay between three phenomena: superconductivity; spin-orbit coupling (which describes the interaction between the intrinsic spin of an electron in a solid and the magnetic field induced by the motion of electron); and a magnetic exchange field (which acts on magnetic spins just like an ordinary magnetic field).
“The choice of material for making such a battery was not a simple matter,” explains team member Andrea Iorio. “In our device, the Al superconducting leads provide the superconductivity, the spin-orbit coupling is an intrinsic property of the InAs nanowire and the magnetic impurities provide the local exchange field.”
While the battery needs to be charged by polarizing the magnetic impurities with an external magnetic field, the researchers say the phase bias between the poles persists even when they later switch the field off. They can control the value of the phase difference either by changing the direction of the polarization of the magnetic impurities or by modifying the length of the semiconducting wires.
Trying out other material combinations
The researchers, who report their work in Nature Nanotechnology, say they are now exploring other material combinations to improve the device’s performance and their ability to control it, as well as making it easier to integrate into quantum circuits.
“One idea we are pushing forward is to use a superconducting wire in contact with a ferromagnetic insulator as a battery,” Iorio explains. “The latter will provide a sizeable exchange field that we can accurately control and we are fabricating and characterizing such a system at the moment.”
The Pisa/San Sebastián research teams are also involved in a European project called SUPERTED that aims to engineer ultrasensitive radiation detectors based on superconductor-ferromagnetic insulator structures, and in particular EuS/Al junctions. “Such systems could be adapted to construct phase batteries with better performance,” Iorio tells Physics World.


physicsworld--2020-07-24--Cosmonaut builds engineered cartilage aboard the International Space Station - Physics World

For the first time , 3D human tissue has been assembled in the microgravity of space .
Through a magnetic levitation device , researchers in Russia , led by Vladislav Parfenov at the Russian Academy of Sciences and 3D Bioprinting Solutions , enabled a cosmonaut aboard the International Space Station ( ISS ) to fabricate human cartilage from a few isolated cells .
Their work could lead to crucial new techniques for regenerating tissues during long-term spaceflight .
Tissue engineering has seen a surge of interest in recent years .
Traditionally , it involves seeding cells onto biocompatible “ scaffolds @ @ @ @ @ @ @ assembled themselves into 3D organs .
However , more flexible , scaffold-free approaches are also emerging , which enable cells to assemble themselves without the need for structural biomaterials .
To do this , researchers use techniques including removable supports , and guiding forces from acoustic and electrostatic fields .
One particularly promising approach involves magnetic levitation , through which strong field gradients can precisely guide tissue cells into place .
To achieve strong enough gradients , however , cells must be suspended within a paramagnetic medium containing gadolinium ions .
At the @ @ @ @ @ @ @ , these ions are toxic to cells , and can cause dangerous pressure imbalances .
One potential solution to this problem is to perform levitated assemblies in microgravity .
Recent studies have shown particular interest in doing this with cartilage – the smooth , elastic tissue found in human joints and intervertebral disks .
Currently , it is poorly understood how cartilage is affected during long-term spaceflight , since space-based experiments are extremely expensive and time-consuming .
In their study , Parfenov and collaborators designed a magnetic bioassembler for use on the ISS @ @ @ @ @ @ @ , non-toxic concentration of gadolinium ions .
To do this , the researchers first fabricated tissue spheroids from human cartilage cells at the Baikonur Cosmodrome in Kazakhstan , which were embedded in heat-reversible hydrogel , then delivered to the ISS in hermetically sealed cuvettes .
After gadolinium ions were injected by a cosmonaut aboard the space station , the cuvettes were cooled to release the cells from the hydrogel , then placed in a 37°C chamber within the bioassembler for two days .
In these conditions , cell fusion and self-assembly could be @ @ @ @ @ @ @ video camera .
Finally , the assembled cartilage was stored at room temperature for two weeks , before being returned to Earth for analysis .
As Parfenov ’ s team hoped , the self-assembly process captured by the camera showed strong agreement with their mathematical models and computer simulations .
The success of their experiment now represents a significant advance in our ability to fabricate 3D human tissues without the need for scaffolds , and with non-toxic levels of gadolinium ions .
With the adverse effects of microgravity on human tissue already well @ @ @ @ @ @ @ prove critical in maintaining the health of astronauts during future manned space exploration .
The research is described in Science Advances .

For the first time, 3D human tissue has been assembled in the microgravity of space. Through a magnetic levitation device, researchers in Russia, led by Vladislav Parfenov at the Russian Academy of Sciences and 3D Bioprinting Solutions, enabled a cosmonaut aboard the International Space Station (ISS) to fabricate human cartilage from a few isolated cells. Their work could lead to crucial new techniques for regenerating tissues during long-term spaceflight.
Tissue engineering has seen a surge of interest in recent years. Traditionally, it involves seeding cells onto biocompatible “scaffolds”, which biodegrade once tissues have assembled themselves into 3D organs. However, more flexible, scaffold-free approaches are also emerging, which enable cells to assemble themselves without the need for structural biomaterials. To do this, researchers use techniques including removable supports, and guiding forces from acoustic and electrostatic fields.
One particularly promising approach involves magnetic levitation, through which strong field gradients can precisely guide tissue cells into place. To achieve strong enough gradients, however, cells must be suspended within a paramagnetic medium containing gadolinium ions. At the concentrations required for the technique to work, these ions are toxic to cells, and can cause dangerous pressure imbalances.
One potential solution to this problem is to perform levitated assemblies in microgravity. Recent studies have shown particular interest in doing this with cartilage – the smooth, elastic tissue found in human joints and intervertebral disks. Currently, it is poorly understood how cartilage is affected during long-term spaceflight, since space-based experiments are extremely expensive and time-consuming. In their study, Parfenov and collaborators designed a magnetic bioassembler for use on the ISS – which would only require a low, non-toxic concentration of gadolinium ions.
To do this, the researchers first fabricated tissue spheroids from human cartilage cells at the Baikonur Cosmodrome in Kazakhstan, which were embedded in heat-reversible hydrogel, then delivered to the ISS in hermetically sealed cuvettes. After gadolinium ions were injected by a cosmonaut aboard the space station, the cuvettes were cooled to release the cells from the hydrogel, then placed in a 37°C chamber within the bioassembler for two days. In these conditions, cell fusion and self-assembly could be sustained, and were recorded on a video camera. Finally, the assembled cartilage was stored at room temperature for two weeks, before being returned to Earth for analysis.
As Parfenov’s team hoped, the self-assembly process captured by the camera showed strong agreement with their mathematical models and computer simulations. The success of their experiment now represents a significant advance in our ability to fabricate 3D human tissues without the need for scaffolds, and with non-toxic levels of gadolinium ions. With the adverse effects of microgravity on human tissue already well known to researchers, their technique could prove critical in maintaining the health of astronauts during future manned space exploration.
The research is described in Science Advances.


physicsworld--2020-07-23--Giant exoplanets directly observed orbiting Sun-like star - Physics World

The first ever direct image of a young Sun-like star accompanied by two giant exoplanets has been captured by astronomers using the Very Large Telescope ( VLT ) in Chile .
The two planets are orbiting the star TYC 8998-760-1 , which lies 300 light-years away from Earth .
The star has an almost identical mass to our Sun , but is just 17 million years old compared with 4.6 billion years for our Sun .
Perhaps the most striking feature of this system is the large mass of the planets and their giant orbits .
The inner planet has @ @ @ @ @ @ @ the outer one six times .
They orbit at distances of roughly 160 and 320 times the Earth–Sun distance respectively , which is more than 30 times larger than the orbits of Jupiter and Saturn .
“ This discovery is a snapshot of an environment that is very similar to our solar system , but at a much earlier stage of its evolution , ” says Alexander Bohn from at Leiden University in the Netherlands , who led the new research , published in Astrophysical Journal Letters .
Bohn told Physics World that @ @ @ @ @ @ @ end of multiple star formation .
In other words , had a bit more stuff accreted from the protostellar cloud , then this could have resulted in a binary star system , rather than one star and two huge planets .
Alternatively , these giant planets could be the result of several small planetessimals clustering together into cores , which eventually gained enough gravitational pull to accrete gas from the circumstellar disc .
This is the favoured scenario for the formation of the largest planets in our own solar system .
“ To @ @ @ @ @ @ @ planets , however , some kind of outward migration is required , ” says Bohn .
“ This can be performed by gravitationally scattering off of each other or with another , so far undetected , third object in the system.
” To date , more than 4000 exoplanets have been detected .
However , the vast majority of these have been spotted using indirect methods , such as observing the dip in starlight as a planet transits between its parent star and our line of sight .
Only a tiny fraction of @ @ @ @ @ @ @ and the direct imaging of two or more exoplanets around the same star is even rarer .
Only two such systems have been directly observed so far , both around stars markedly different from our Sun .
These latest images were possible due to the SPHERE instrument on the VLT at the European Southern Observatory ( ESO ) in Chile , which uses a coronagraph to block bright starlight , allowing much fainter planets to be seen .
While older planets , such as those seen in our solar system , are too @ @ @ @ @ @ @ , young planets are hotter , and so glow brighter in infrared light .
“ This discovery still tells us that there is not just one way to form a planetary system , and the outcome of the process can be very different , ” says Carlo Felice Manara , an astronomer based at ESO headquarters in Germany , who was not involved in this latest research .
“ Why in our solar system we only have planets with mass of Jupiter , or less , and no more massive planets is still @ @ @ @ @ @ @ TYC 8998-760-1 system will enable astronomers to better understand its dynamics .
ESO ’ s Extremely Large Telescope – scheduled to capture its first astronomical images in 2025 – could even detect further planets with Neptune or Saturn masses .
Unfortunately , even that instrument is unlikely to detect rocky planets similar to Earth , as these are just too faint .

Caught on camera: This first-ever image of a multi-planet system around a Sun-like star shows the two planets (centre and bottom right) orbiting TYC 8998-760-1 (Courtesy: ESO/Bohn et al.)
The first ever direct image of a young Sun-like star accompanied by two giant exoplanets has been captured by astronomers using the Very Large Telescope (VLT) in Chile. The two planets are orbiting the star TYC 8998-760-1, which lies 300 light-years away from Earth. The star has an almost identical mass to our Sun, but is just 17 million years old compared with 4.6 billion years for our Sun.
Perhaps the most striking feature of this system is the large mass of the planets and their giant orbits. The inner planet has 14 times Jupiter’s mass and the outer one six times. They orbit at distances of roughly 160 and 320 times the Earth–Sun distance respectively, which is more than 30 times larger than the orbits of Jupiter and Saturn.
This discovery is a snapshot of an environment that is very similar to our solar system, but at a much earlier stage of its evolution. Alexander Bohn, Leiden University
“This discovery is a snapshot of an environment that is very similar to our solar system, but at a much earlier stage of its evolution,” says Alexander Bohn from at Leiden University in the Netherlands, who led the new research, published in Astrophysical Journal Letters.
A turbulent past
Bohn told Physics World that this system might represent the lower mass end of multiple star formation. In other words, had a bit more stuff accreted from the protostellar cloud, then this could have resulted in a binary star system, rather than one star and two huge planets.
Alternatively, these giant planets could be the result of several small planetessimals clustering together into cores, which eventually gained enough gravitational pull to accrete gas from the circumstellar disc. This is the favoured scenario for the formation of the largest planets in our own solar system.
“To explain the large separations of our detected planets, however, some kind of outward migration is required,” says Bohn. “This can be performed by gravitationally scattering off of each other or with another, so far undetected, third object in the system.”
To date, more than 4000 exoplanets have been detected. However, the vast majority of these have been spotted using indirect methods, such as observing the dip in starlight as a planet transits between its parent star and our line of sight.
Only a tiny fraction of these planets has been directly observed, and the direct imaging of two or more exoplanets around the same star is even rarer. Only two such systems have been directly observed so far, both around stars markedly different from our Sun.
Hot young planets
These latest images were possible due to the SPHERE instrument on the VLT at the European Southern Observatory (ESO) in Chile, which uses a coronagraph to block bright starlight, allowing much fainter planets to be seen. While older planets, such as those seen in our solar system, are too cool to be found with this technique, young planets are hotter, and so glow brighter in infrared light.
This discovery still tells us that there is not just one way to form a planetary system. Carlo Felice Manara, European Southern Observatory
“This discovery still tells us that there is not just one way to form a planetary system, and the outcome of the process can be very different,” says Carlo Felice Manara, an astronomer based at ESO headquarters in Germany, who was not involved in this latest research. “Why in our solar system we only have planets with mass of Jupiter, or less, and no more massive planets is still an open question.”
Further observations of TYC 8998-760-1 system will enable astronomers to better understand its dynamics. ESO’s Extremely Large Telescope – scheduled to capture its first astronomical images in 2025 – could even detect further planets with Neptune or Saturn masses. Unfortunately, even that instrument is unlikely to detect rocky planets similar to Earth, as these are just too faint.


physicsworld--2020-07-23--Caution required when balancing lung versus heart radiotherapy dose - Physics World

As treatments for oesophageal cancer improve , patients are living longer , especially those with early-stage localized disease .
But longer survival puts oesophageal cancer patients at greater risk of developing serious radiation-induced late toxicities of the heart and lung .
The lack of predictive models , such as those developed for breast cancer patients , has hampered the design of clinically effective radiotherapy treatment plans that also reduce heart and lung toxicity .
And because radiation dose to the heart is generally much higher when treating oesophageal cancer , breast cancer models are not automatically transferable .
Planning radiotherapy @ @ @ @ @ @ @ the fact that reducing radiation dose to the heart increases the potential for lung toxicity .
The optimal balance between cardiac and pulmonary toxicities and their influence on overall survival is unknown , according to researchers at the University Medical Center Groningen in the Netherlands and the Osaka Medical Center for Cancer and Cardiovascular Disease in Japan .
To evaluate which clinical and dosimetric parameters are associated with cardiac and/or pulmonary toxicities , the team conducted a retrospective study of 219 oesophageal cancer patients who received 3D conformal radiotherapy .
Reporting their results @ @ @ @ @ @ @ determined that radiation dose to the lungs significantly impacted overall survival .
Because of this outcome , they state that reducing cardiac dose at the expense of dose to the lungs “ might not always be a good strategy , ” especially when using intensity-modulated radiotherapy ( IMRT ) or volumetric-modulated arc therapy ( VMAT ) .
The study cohort included patients with all stages of oesophageal cancer who underwent radiotherapy at the Osaka Medical Center between 2007 and 2013 .
Patients ranged in age from 40 to 88 years , were predominantly @ @ @ @ @ @ @ ( 86 % ) and drank alcohol ( 89 % ) .
Eighteen percent had a personal ( 12 % ) or family ( 6 % ) history of cardiovascular disease .
Only 12 % were diabetics and only 7 % were overweight .
Patients were treated using 10 MV photons in 1.8–2.0 Gy daily fractions to a total dose of 50.4–66.0 Gy ( median : 60 Gy ) .
They had follow-up visits every three to six months for the first two years , and semi-annually thereafter .
With a median follow-up @ @ @ @ @ @ @ patients had developed locoregional failures .
The median disease-free survival was 64 months .
The researchers measured dose–volume parameters including dose to the whole heart , and substructures of the heart and lungs , and mean doses .
They also recorded all newly diagnosed cardiac and pulmonary events .
They reported that 28 % of patients developed radiation-induced pneumonitis .
The primary predictor of radiation pneumonitis was mean lung dose .
The patients who developed radiation pneumonitis had significantly worse overall survival compared with other study participants .
Roughly one third of the @ @ @ @ @ @ @ of excess fluid in the pericardium that puts pressure on the heart and can lead to heart failure .
However , this toxicity did not seem to influence overall survival in the patient cohort .
Multivariable analysis revealed that radiation dose to the lungs ( V45 , the volume of lung receiving over 45 Gy ) , but not the dose to the heart , influenced overall survival significantly in these patients .
When the team repeated the analyses excluding patients with radiation pneumonitis , the same variables remained significant .
In the @ @ @ @ @ @ @ important predictor for overall survival was the radiation dose to the heart .
“ Cardiac dose–volume parameters predicted the risk of pericardial effusion and pulmonary dose–volume parameters predicted the risk of radiation pneumonitis , ” write the authors .
“ However , in this patient cohort , pulmonary DVH parameters ( V45 ) were more important for overall survival than cardiac DVH parameters.
” Because worse overall survival can be caused by radiation dose to both organs-at-risk , the authors suggest that oesophageal cancer patients are treated with proton therapy , because it @ @ @ @ @ @ @ the heart and to the lungs .
First author Jannet Beukema tells Physics World that the University Medical Center Groningen is now utilizing proton therapy for preoperative oesophageal cancer patients .
They are currently conducting more research to determine heart and lung toxicity in this patient group .

Oesophageal radiotherapy calls for a fine balancing act between dose to the heart and dose to the lungs. (Courtesy: iStock/leonello)
As treatments for oesophageal cancer improve, patients are living longer, especially those with early-stage localized disease. But longer survival puts oesophageal cancer patients at greater risk of developing serious radiation-induced late toxicities of the heart and lung.
The lack of predictive models, such as those developed for breast cancer patients, has hampered the design of clinically effective radiotherapy treatment plans that also reduce heart and lung toxicity. And because radiation dose to the heart is generally much higher when treating oesophageal cancer, breast cancer models are not automatically transferable.
Planning radiotherapy for oesophageal cancer is further complicated by the fact that reducing radiation dose to the heart increases the potential for lung toxicity. The optimal balance between cardiac and pulmonary toxicities and their influence on overall survival is unknown, according to researchers at the University Medical Center Groningen in the Netherlands and the Osaka Medical Center for Cancer and Cardiovascular Disease in Japan.
To evaluate which clinical and dosimetric parameters are associated with cardiac and/or pulmonary toxicities, the team conducted a retrospective study of 219 oesophageal cancer patients who received 3D conformal radiotherapy. Reporting their results in Radiotherapy and Oncology, the researchers determined that radiation dose to the lungs significantly impacted overall survival. Because of this outcome, they state that reducing cardiac dose at the expense of dose to the lungs “might not always be a good strategy,” especially when using intensity-modulated radiotherapy (IMRT) or volumetric-modulated arc therapy (VMAT).
The study cohort included patients with all stages of oesophageal cancer who underwent radiotherapy at the Osaka Medical Center between 2007 and 2013. Patients ranged in age from 40 to 88 years, were predominantly male (83%), smokers (86%) and drank alcohol (89%). Eighteen percent had a personal (12%) or family (6%) history of cardiovascular disease. Only 12% were diabetics and only 7% were overweight.
Patients were treated using 10 MV photons in 1.8–2.0 Gy daily fractions to a total dose of 50.4–66.0 Gy (median: 60 Gy). They had follow-up visits every three to six months for the first two years, and semi-annually thereafter. With a median follow-up of 27 months, 45% of patients had developed locoregional failures. The median disease-free survival was 64 months.
The researchers measured dose–volume parameters including dose to the whole heart, and substructures of the heart and lungs, and mean doses. They also recorded all newly diagnosed cardiac and pulmonary events. They reported that 28% of patients developed radiation-induced pneumonitis. The primary predictor of radiation pneumonitis was mean lung dose. The patients who developed radiation pneumonitis had significantly worse overall survival compared with other study participants.
Roughly one third of the patients developed pericardial effusion, the build-up of excess fluid in the pericardium that puts pressure on the heart and can lead to heart failure. However, this toxicity did not seem to influence overall survival in the patient cohort.
Multivariable analysis revealed that radiation dose to the lungs (V45, the volume of lung receiving over 45 Gy), but not the dose to the heart, influenced overall survival significantly in these patients. When the team repeated the analyses excluding patients with radiation pneumonitis, the same variables remained significant. In the patients with radiation pneumonitis, the most important predictor for overall survival was the radiation dose to the heart.
“Cardiac dose–volume parameters predicted the risk of pericardial effusion and pulmonary dose–volume parameters predicted the risk of radiation pneumonitis,” write the authors. “However, in this patient cohort, pulmonary DVH parameters (V45) were more important for overall survival than cardiac DVH parameters.”
Because worse overall survival can be caused by radiation dose to both organs-at-risk, the authors suggest that oesophageal cancer patients are treated with proton therapy, because it can reduce both the radiation dose to the heart and to the lungs. First author Jannet Beukema tells Physics World that the University Medical Center Groningen is now utilizing proton therapy for preoperative oesophageal cancer patients. They are currently conducting more research to determine heart and lung toxicity in this patient group.


physicsworld--2020-07-23--China successfully launches Tianwen-1 Mars probe - Physics World

China has launched its first independent mission to Mars with the uncrewed craft expected to look for clues of water-ice , past life and study the evolution of our neighbouring planet .
At 12:41 p.m. Beijing time today , Tianwen-1 ( “ heavenly questions ” ) took off atop a Long March 5 rocket from Wenchang Satellite Launch Center in southern China .
The craft contains an orbiter as well as a lander and rover and is expected to reach Mars in February .
China Aerospace Science and Technology Corporation ( CASC ) – the country ’ s main space @ @ @ @ @ @ @ smoothly and about 45 minutes later the probe entered the planned Earth–Mars transfer orbit .
“ [ Tianwen-1 is ] a milestone mission for China ’ s aerospace to go deeper into space , ” noted mission deputy commander Yansheng Wu in a statement .
Onboard Tianwen-1 are 13 scientific instruments – seven on the orbiter and six on the rover – that will aim to obtain comprehensive , first-hand data about the planet including its magnetosphere and atmosphere as well as surface and subsurface geological structures .
Some instruments on Tianwen-1 are @ @ @ @ @ @ @ missions , such as a surface component detector that fires a laser to vaporize rock surfaces and measure chemical elements as well as ground-penetrating radar to detect global water-ice distribution from orbit .
Landing on Mars will be China ’ s next challenge .
Despite its recent successes with a Moon landing , China has never landed through a thin atmosphere like that on Mars .
To do so , Tianwen-1 will use a parachute and a “ retro-engine ” to slow down its descent .
At about 100 m above the surface @ @ @ @ @ @ @ retro engines to take snapshots of the landing area to calculate the best landing spot .
To manage this aspect of the landing , the craft will use an autonomous obstacle avoidance technology , which was originally developed for China ’ s lunar missions .
It is hoped that the lander and rover will touch down in a region called Utopia Planitia , which is a largely flat impact basin but scientifically interesting with potential water-ice underneath .
China ’ s first attempt to reach Mars was in 2011 when an orbiter piggybacked @ @ @ @ @ @ @ moon Phobos .
However , the launch failed and China began to come up with a new mission .
The successful launch of Tianwen-1 greatly boosts confidence in the Long March 5 rocket – China ’ s biggest heavy-lifting launcher – after it experienced a major failure in 2017 due to a first-stage engine problem .
This success has now paved the way for a sample-return mission to the Moon by the end of the year as well as the launch of the core module of the Chinese space station early next year @ @ @ @ @ @ @ heading to Mars this month .
On Monday , the United Arab Emirates successfully launched its Mars-bound Hope orbiter from Japan while on 30 July NASA is expected to launch its Mars 2020 mission , which includes the Perseverance rover and a Mars helicopter called Ingenuity .

Mars bound: China's Tianwen-1 mission, which launched today, will study Mars’ magnetosphere and atmosphere as well as surface and subsurface geological structures. (Courtesy: CASTC)
China has launched its first independent mission to Mars with the uncrewed craft expected to look for clues of water-ice, past life and study the evolution of our neighbouring planet. At 12:41 p.m. Beijing time today, Tianwen-1 (“heavenly questions”) took off atop a Long March 5 rocket from Wenchang Satellite Launch Center in southern China. The craft contains an orbiter as well as a lander and rover and is expected to reach Mars in February.
[Tianwen-1 is] a milestone mission for China’s aerospace to go deeper into space Yansheng Wu
China Aerospace Science and Technology Corporation (CASC) – the country’s main space contractor – said that the launch went smoothly and about 45 minutes later the probe entered the planned Earth–Mars transfer orbit. “[Tianwen-1 is] a milestone mission for China’s aerospace to go deeper into space,” noted mission deputy commander Yansheng Wu in a statement.
Onboard Tianwen-1 are 13 scientific instruments – seven on the orbiter and six on the rover – that will aim to obtain comprehensive, first-hand data about the planet including its magnetosphere and atmosphere as well as surface and subsurface geological structures. Some instruments on Tianwen-1 are similar to those used in previous NASA missions, such as a surface component detector that fires a laser to vaporize rock surfaces and measure chemical elements as well as ground-penetrating radar to detect global water-ice distribution from orbit.
Confidence boost
Landing on Mars will be China’s next challenge. Despite its recent successes with a Moon landing, China has never landed through a thin atmosphere like that on Mars. To do so, Tianwen-1 will use a parachute and a “retro-engine” to slow down its descent. At about 100 m above the surface, Tianwen-1 will briefly pause firing its retro engines to take snapshots of the landing area to calculate the best landing spot. To manage this aspect of the landing, the craft will use an autonomous obstacle avoidance technology, which was originally developed for China’s lunar missions. It is hoped that the lander and rover will touch down in a region called Utopia Planitia, which is a largely flat impact basin but scientifically interesting with potential water-ice underneath.
China’s first attempt to reach Mars was in 2011 when an orbiter piggybacked on a Russian mission to the Martian moon Phobos. However, the launch failed and China began to come up with a new mission. The successful launch of Tianwen-1 greatly boosts confidence in the Long March 5 rocket – China’s biggest heavy-lifting launcher – after it experienced a major failure in 2017 due to a first-stage engine problem. This success has now paved the way for a sample-return mission to the Moon by the end of the year as well as the launch of the core module of the Chinese space station early next year.
Tianwen-1 is one of three missions heading to Mars this month. On Monday, the United Arab Emirates successfully launched its Mars-bound Hope orbiter from Japan while on 30 July NASA is expected to launch its Mars 2020 mission, which includes the Perseverance rover and a Mars helicopter called Ingenuity.


physicsworld--2020-07-23--Fluid flow and stress cause tiny marine organisms to emit light - Physics World

New research by Raymond Goldstein and colleagues at the University of Cambridge has revealed how fluid motion and direct mechanical pressure triggers the emission of bioluminescent light by tiny marine organisms .
Bioluminescence occurs in a wide array of organisms including dinoflagellates , which are single-celled plankton that play a crucial role in aquatic food chains .
Despite their global importance , scientists do not have a full understanding of how these organisms emit green-blue light in response to fluid motion in their environments .
Goldstein ’ s team looked at how the light intensity from dinoflagellates correlates with various @ @ @ @ @ @ @ exposing the tiny organisms to two types of stimuli mimicking the mechanical attack of a predator and swimming in a densely populated wave .
The team built their study upon previous work by Michael Latz and colleagues at the Scripps Institution of Oceanography in the US .
Latz ’ s team had used macroscopic contracting fl0ws , Couette flow , microfluidic flows , and atomic force microscopy to study dinoflagellates .
“ Our work is the next logical step that builds on [ Latz ’ s ] work , by using micropipette technology @ @ @ @ @ @ @ cell wall deformations , all with high-speed imaging , ” explains Goldstein .
The bioluminescence of dinoflagellates is unique from many perspectives .
The biochemical and cellular cascade leading to a light flash begins when the cell membrane is subject to mechanical stress , which activates a receptor in the membrane .
This mechanical signal is translated into an electrical signal by increasing the concentration of calcium ions .
As a result , membranes of inner organelles depolarize and generate an action potential that propagates along the membranes .
Ultimately , the pH @ @ @ @ @ @ @ oxidation catalyzed by luciferase , which is accompanied by a photon release .
To investigate the underlying biophysical processes , Goldstein and his team held single cells of the dinoflagellate Pyrocystis lunula on a glass micropipette using suction .
Measuring 30–1000 μm , they are ideal experimental subjects thanks to their robustness and reduced motility .
According to Goldstein , the team often manipulated each cell up to 20 times without any obvious damage .
The cells were mechanically stimulated either by directing a submerged jet of fluid ( growth medium ) at @ @ @ @ @ @ @ single cell between two pipettes with submicron precision .
The cell wall deformation was monitored by direct imaging with a high-speed camera .
The results showed that the cells flash only after the fluid pressure is high enough to induce significant cell wall deformation .
The flash occurs and decays within fractions of a second .
The bioluminescence intensity eventually decreases , most probably due to exhaustion of the luciferin .
Interestingly , bioluminescence tends to occur within the central region around the cell ’ s nucleus .
For mechanical stimuli , light @ @ @ @ @ @ @ small ( whatever the speed ) , or when the deformation rate was small ( whatever the deformation ) .
However , the bioluminescence flash was large when both the deformation and its rate were large .
These results suggest that the membrane and calcium channels have viscoelastic properties – which was confirmed by a phenomenological model .
According to Latz , “ this study provides a welcome contribution to our knowledge of mechanosensory responsiveness in the dinoflagellate bioluminescence system .
I applaud their use of controlled and quantified modes of mechanical stimulation @ @ @ @ @ @ @ of our challenges is the discrepancy between sensitivity in macroflows and microstimulation , based on the as-yet unknown distribution of mechanosensors within the cell and how their activity is integrated into a whole cell response .
As I am now retired , I hope that it will inspire others to continue the work , ” Latz adds .
Goldstein adds “ Michael Latz has shown , already a number of years ago , that dinoflagellates can be used as local sensors for fluid shear .
We are now very interested in the role @ @ @ @ @ @ @ extending our understanding of cell wall mechanics , and in force and light distribution over the entire cell body.
” The research is described in Physical Review Letters .

Light of the moon: a dinoflagellate seen under a microscope. Its crescent shape is bounded by a cell wall. The central orange regions are cell nuclei and bioluminescence originates in vesicles surrounding these nuclei when the cell walls are deformed. (Courtesy: Maziyar Jalaal, Nico Schramma, Antoine Dode, Hélène de Maleprade, Christophe Raufaste and Raymond E Goldstein/University of Cambridge)
New research by Raymond Goldstein and colleagues at the University of Cambridge has revealed how fluid motion and direct mechanical pressure triggers the emission of bioluminescent light by tiny marine organisms.
Bioluminescence occurs in a wide array of organisms including dinoflagellates, which are single-celled plankton that play a crucial role in aquatic food chains. Despite their global importance, scientists do not have a full understanding of how these organisms emit green-blue light in response to fluid motion in their environments.
Goldstein’s team looked at how the light intensity from dinoflagellates correlates with various mechanical stressors. They did this by exposing the tiny organisms to two types of stimuli mimicking the mechanical attack of a predator and swimming in a densely populated wave.
The team built their study upon previous work by Michael Latz and colleagues at the Scripps Institution of Oceanography in the US. Latz’s team had used macroscopic contracting fl0ws, Couette flow, microfluidic flows, and atomic force microscopy to study dinoflagellates.
“Next logical step”
“Our work is the next logical step that builds on [Latz’s] work, by using micropipette technology to hold individual cells and apply quantified cell wall deformations, all with high-speed imaging,” explains Goldstein.
The bioluminescence of dinoflagellates is unique from many perspectives. The biochemical and cellular cascade leading to a light flash begins when the cell membrane is subject to mechanical stress, which activates a receptor in the membrane. This mechanical signal is translated into an electrical signal by increasing the concentration of calcium ions.
As a result, membranes of inner organelles depolarize and generate an action potential that propagates along the membranes. Ultimately, the pH of the environment decreases, promoting luciferin oxidation catalyzed by luciferase, which is accompanied by a photon release.
Ideal experimental subjects
To investigate the underlying biophysical processes, Goldstein and his team held single cells of the dinoflagellate Pyrocystis lunula on a glass micropipette using suction. Measuring 30–1000 μm, they are ideal experimental subjects thanks to their robustness and reduced motility. According to Goldstein, the team often manipulated each cell up to 20 times without any obvious damage.
The cells were mechanically stimulated either by directing a submerged jet of fluid (growth medium) at a single cell or by squeezing a single cell between two pipettes with submicron precision. The cell wall deformation was monitored by direct imaging with a high-speed camera.
The results showed that the cells flash only after the fluid pressure is high enough to induce significant cell wall deformation. The flash occurs and decays within fractions of a second. The bioluminescence intensity eventually decreases, most probably due to exhaustion of the luciferin. Interestingly, bioluminescence tends to occur within the central region around the cell’s nucleus.
For mechanical stimuli, light intensity was low when the deformation was small (whatever the speed), or when the deformation rate was small (whatever the deformation). However, the bioluminescence flash was large when both the deformation and its rate were large. These results suggest that the membrane and calcium channels have viscoelastic properties – which was confirmed by a phenomenological model.
“Welcome contribution”
According to Latz, “this study provides a welcome contribution to our knowledge of mechanosensory responsiveness in the dinoflagellate bioluminescence system. I applaud their use of controlled and quantified modes of mechanical stimulation using sophisticated analytical techniques.”
“One of our challenges is the discrepancy between sensitivity in macroflows and microstimulation, based on the as-yet unknown distribution of mechanosensors within the cell and how their activity is integrated into a whole cell response. As I am now retired, I hope that it will inspire others to continue the work,” Latz adds.
Goldstein adds “Michael Latz has shown, already a number of years ago, that dinoflagellates can be used as local sensors for fluid shear. We are now very interested in the role of dinoflagellates in algal blooms, in extending our understanding of cell wall mechanics, and in force and light distribution over the entire cell body.”
The research is described in Physical Review Letters.


physicsworld--2020-07-23--Nanostructured topological insulator growth speeds up - Physics World

A supportive “ mattress ” of material has made it possible to grow nanoribbons of a previously hard-to-synthesize topological insulator .
The technique , which is based on conventional chemical vapour transport , produces crystalline nanostructures of zirconium pentatelluride ( ZrTe ) with a high carrier mobility , and could be used to produce ultrathin and even monolayer ZrTe in the future .
Topological insulators are materials that act as electrical insulators in their bulk , while conducting electricity extremely well on their surfaces ( or edges ) via special , topologically protected , electronic states .
Within these states @ @ @ @ @ @ @ direction and do not backscatter .
This remarkable behaviour allows the materials to carry electrical current with near-zero dissipation – meaning that they could someday be used to make electronic devices that are far more energy-efficient than any that exist today .
Even within this exotic family of materials , ZrTe stands out thanks to its wide variety of topological phases .
Depending on how it is configured , it can behave as a weak or a strong insulator , a Dirac semimetal or a 3D quantum Hall state .
When thinned down @ @ @ @ @ @ @ predicted to be a large band gap quantum spin Hall insulator .
Previous studies of ZrTe mainly focused on its 3D bulk form .
For real-world applications , however , nanowires or nanoribbons may be more useful , as surface states play a more important role when the surface-to-volume ratio is higher .
New electronic properties could also emerge .
Research on other types of nanostructured topological insulators has already revealed unexpected phases , and novel phenomena called “ Majorana zero modes ” ( which could be used as bits in quantum computers @ @ @ @ @ @ @ time when indium antimonide ( InSb ) nanowires were combined with superconductors .
Until the present work , efforts to grow high-quality nanostructures of ZrTe had foundered for lack of a reliable way to produce them quickly or in large-enough quantities .
The new technique developed by Xiaosong Wu and colleagues of Peking University and South University of Science and Technology of China in Shenzhen is based on conventional chemical vapour transport .
Here , source materials such as zirconium and tellurium react in their gas phases with the help of a transport @ @ @ @ @ @ @ ) and crystallize .
“ The only difference between our technique and the conventional method is the introduction of silicon , which allows for the growth of nanostructured ZrTe , ” Wu explains .
The ZrTe nanostructures do not grow directly on the silicon substrate , Wu adds .
Instead , they develop out of a “ mattress ” that mainly consists of Zr and Te in a ratio of around 1:3 .
Wu thinks this ZrTe mattress may provide a more suitable substrate for ZrTe to grow on .
Certainly , when @ @ @ @ @ @ @ the mattress ’ edge , they observed etches in the silicon substrate .
“ We know that iodine reacts with silicon and forms SiI , which is in the gaseous phase at the growth temperature we employed , ” says Wu .
“ We found that silicon plays an important role in the reaction but we are as yet unsure on how it affects the growth process exactly.
” The researchers say they can also grow millimetre-long single crystals in around two hours – a huge improvement on conventional methods , which require @ @ @ @ @ @ @ aberration-corrected transmission electron microscopy ( TEM ) images of the as-grown ZrTe nanoribbons suggest that the structures are highly crystalline .
Quantum transport measurements also show that they contain few impurities and that they have a high carrier mobility of over 30,000 cm2/Vs – meaning that they conduct electricity extremely well .
“ Our method shows great promise for growing high-quality ultra-thin nanostructures of ZrTe and even monolayers , ” Wu tells Physics World .
“ Being able to do so would allow us to make this large band gap quantum spin Hall @ @ @ @ @ @ @ fundamental physical properties in experiments.
” The researchers , who report their work in Chinese Physics B , say they are now busy improving their technique so they can grow thinner nanostructures .

Growth of ZrTe 5 nanostructures. (Courtesy: Chin. Phys. B)
A supportive “mattress” of material has made it possible to grow nanoribbons of a previously hard-to-synthesize topological insulator. The technique, which is based on conventional chemical vapour transport, produces crystalline nanostructures of zirconium pentatelluride (ZrTe 5 ) with a high carrier mobility, and could be used to produce ultrathin and even monolayer ZrTe 5 in the future.
Topological insulators are materials that act as electrical insulators in their bulk, while conducting electricity extremely well on their surfaces (or edges) via special, topologically protected, electronic states. Within these states, electrons can only travel in one direction and do not backscatter. This remarkable behaviour allows the materials to carry electrical current with near-zero dissipation – meaning that they could someday be used to make electronic devices that are far more energy-efficient than any that exist today.
Even within this exotic family of materials, ZrTe 5 stands out thanks to its wide variety of topological phases. Depending on how it is configured, it can behave as a weak or a strong insulator, a Dirac semimetal or a 3D quantum Hall state. When thinned down to a monolayer, it is also predicted to be a large band gap quantum spin Hall insulator.
Topological nanoribbons
Previous studies of ZrTe 5 mainly focused on its 3D bulk form. For real-world applications, however, nanowires or nanoribbons may be more useful, as surface states play a more important role when the surface-to-volume ratio is higher. New electronic properties could also emerge. Research on other types of nanostructured topological insulators has already revealed unexpected phases, and novel phenomena called “Majorana zero modes” (which could be used as bits in quantum computers) were observed experimentally for the first time when indium antimonide (InSb) nanowires were combined with superconductors.
Until the present work, efforts to grow high-quality nanostructures of ZrTe 5 had foundered for lack of a reliable way to produce them quickly or in large-enough quantities. The new technique developed by Xiaosong Wu and colleagues of Peking University and South University of Science and Technology of China in Shenzhen is based on conventional chemical vapour transport. Here, source materials such as zirconium and tellurium react in their gas phases with the help of a transport agent (iodine, in this case) and crystallize. “The only difference between our technique and the conventional method is the introduction of silicon, which allows for the growth of nanostructured ZrTe 5 ,” Wu explains.
Silicon plays an important role in growth
The ZrTe 5 nanostructures do not grow directly on the silicon substrate, Wu adds. Instead, they develop out of a “mattress” that mainly consists of Zr and Te in a ratio of around 1:3.
Wu thinks this ZrTe 3 mattress may provide a more suitable substrate for ZrTe 5 to grow on. Certainly, when he and his colleagues looked closer at the mattress’ edge, they observed etches in the silicon substrate. “We know that iodine reacts with silicon and forms SiI 4 , which is in the gaseous phase at the growth temperature we employed,” says Wu. “We found that silicon plays an important role in the reaction but we are as yet unsure on how it affects the growth process exactly.”
The researchers say they can also grow millimetre-long single crystals in around two hours – a huge improvement on conventional methods, which require weeks.
Growing thinner nanostructures
According to the team, aberration-corrected transmission electron microscopy (TEM) images of the as-grown ZrTe 5 nanoribbons suggest that the structures are highly crystalline. Quantum transport measurements also show that they contain few impurities and that they have a high carrier mobility of over 30,000 cm2/Vs – meaning that they conduct electricity extremely well.
“Our method shows great promise for growing high-quality ultra-thin nanostructures of ZrTe 5 and even monolayers,” Wu tells Physics World. “Being able to do so would allow us to make this large band gap quantum spin Hall insulator in the laboratory and study its fundamental physical properties in experiments.”
The researchers, who report their work in Chinese Physics B, say they are now busy improving their technique so they can grow thinner nanostructures.


physicsworld--2020-07-23--A flat-Earth fight, an inconsistent Hubble constant, and carbon atoms at a graphene ‘watering hole’

A flat-Earth fight, an inconsistent Hubble constant, and carbon atoms at a graphene ‘watering hole’ - Physics World

This episode of the Physics World Weekly podcast explores two very different scientific debates : one about the shape of the Earth , and the other about the expansion of the universe .
Scientifically speaking , the “ debate ” about the Earth ’ s shape was settled hundreds ( perhaps even thousands ) of years ago : our planet is round , an “ oblate spheroid ” squashed at its poles and bulging at its equator .
But that hasn ’ t deterred some people from believing it ’ s a flat disc , and their numbers seem to @ @ @ @ @ @ @ the science writer Rachel Brazil , whose feature article “ Fighting flat-Earth theory ” appears in the July issue of Physics World , modern flat-Earthism is driven by a wider tendency towards conspiracy-mindedness , with considerable crossover between flat-Earth beliefs and other , unrelated conspiracy theories such as climate-change denial and the anti-vaccination movement .
Because of this , Brazil suggests that “ arguing the physics ” may not actually be the best way to change minds .
“ With people who are so untrusting , they will just see everything as a @ @ @ @ @ @ @ editor-in-chief Matin Durrani .
As for the expansion of the universe , this debate is , mercifully , less heated .
It centres on the fact that the Hubble constant , which characterizes the speed of the universe ’ s expansion , has been measured in two ways .
The first , “ local ” method relies on measuring the intrinsic brightness of certain stellar objects ( known as “ standard candles ” ) .
The second , “ global ” method is based on measurements of the cosmic microwave background radiation .
@ @ @ @ @ @ @ , these methods produce different – and incompatible – values for how fast the universe is expanding .
You can find out more about this discrepancy ( and how to resolve it ) in Cooper ’ s feature “ Finding a consistent constant ” , and in a related video .

This episode of the Physics World Weekly podcast explores two very different scientific debates: one about the shape of the Earth, and the other about the expansion of the universe.
Scientifically speaking, the “debate” about the Earth’s shape was settled hundreds (perhaps even thousands) of years ago: our planet is round, an “oblate spheroid” squashed at its poles and bulging at its equator. But that hasn’t deterred some people from believing it’s a flat disc, and their numbers seem to be on the rise. According to the science writer Rachel Brazil, whose feature article “Fighting flat-Earth theory” appears in the July issue of Physics World, modern flat-Earthism is driven by a wider tendency towards conspiracy-mindedness, with considerable crossover between flat-Earth beliefs and other, unrelated conspiracy theories such as climate-change denial and the anti-vaccination movement. Because of this, Brazil suggests that “arguing the physics” may not actually be the best way to change minds. “With people who are so untrusting, they will just see everything as a hoax,” she tells Physics World editor-in-chief Matin Durrani.
As for the expansion of the universe, this debate is, mercifully, less heated. It centres on the fact that the Hubble constant, which characterizes the speed of the universe’s expansion, has been measured in two ways. The first, “local” method relies on measuring the intrinsic brightness of certain stellar objects (known as “standard candles”). The second, “global” method is based on measurements of the cosmic microwave background radiation. As the science writer Keith Cooper explains, these methods produce different – and incompatible – values for how fast the universe is expanding. You can find out more about this discrepancy (and how to resolve it) in Cooper’s feature “Finding a consistent constant”, and in a related video.


physicsworld--2020-07-23--Cryogenic innovation: ramping up research productivity at ultralow temperatures - Physics World

ICEoxford , as the name suggests , is in the business of keeping things cold – ultracold to be precise .
As such , the UK-based designer and manufacturer of specialist cryogenic systems supports fundamental and applied research efforts across a diverse customer base – from neutron and X-ray beamline scientists to quantum computing start-ups ; from scanning-probe microscopy specialists to physicists studying the fundamental properties of high-temperature superconductors .
“ Generally , our customers want to get cold , get cold as quickly as possible , plus many want the option of studying their samples within a magnetic field @ @ @ @ @ @ @ Technical Officer at ICEoxford .
With those requirements in mind , Kelly and his colleagues in Oxfordshire have pioneered the DRY ICE 1.5K 100 mm , a closed-loop cryostat that enables users to carry out experiments in the temperature range from 1.3 K to 325 K while ensuring tight tolerance on temperature stability ( ±10 mK below 10 K ) , fast cool-down times ( < 30 min to 1.4 K ) and minimal vibration in the sample space ( as little as ±100 nm ) .
There ’ s also the option @ @ @ @ @ @ @ achieve even lower temperatures ( 300 mK and 15 mK respectively ) .
Kelly , for his part , is keen to emphasize the win-win of a 100 mm diameter sample space matched with the cryostat ’ s high-cooling-power capability ( > 30 mW at 1.75 K ) .
“ This is the largest available sample space and highest cooling power on the market for a variable-temperature-insert [ VTI ] cryostat , ” he claims .
Equally significant is the fast-track cool-down cycle – and particularly so for scientists allocated time on the @ @ @ @ @ @ @ Neutron and Muon Source or the Diamond Light Source ( both also in Oxfordshire ) .
“ Beam time is expensive and scientific users only get a fixed slot to complete their experiments – typically just a few days , ” adds Kelly .
Smaller laboratories also benefit , with the rapid cool-down translating into enhanced productivity versus research output ( e.g .
fast sample pre-testing in the cryogenic systems of quantum computers ) .
Given the varied , often unique , requirements of ICEoxford ’ s end-users , the vendor sets a @ @ @ @ @ @ @ and manufacturing teams .
Their task , says Kelly , is to bring a versatility of approach to all customer relationships , with a relentless focus on delivering the best system to do the job .
“ We work closely with the customer to fully understand their requirements and will tailor the product design to meet their exact specifications , ” he notes .
The DRY ICE 1.5K 100 mm provides a case study in versatility , not least in terms of its vibration performance .
The system can utilize two types of @ @ @ @ @ @ @ set-up ( which relies on a mobile piston for compression and expansion of the helium fluid in the cold-head ) or pulse-tube refrigerator ( PTR ) technology ( with no moving parts in the low-temperature region ) .
“ Most users don ’ t see vibration as a show-stopper , ” says Kelly , “ but those who do are likely to choose PTR cooling , as the vibration is approaching an order of magnitude lower than GM.
” Further damping comes with the use of so-called “ ICE sock ” technology , @ @ @ @ @ @ @ a range of ICEoxford products .
“ Put simply , ” explains Kelly , “ we build a container called a sock to surround the cryocooler .
We then load the cooler into the sock and hold it away from any mechanical parts on a bellows.
” A range of anti-vibration frames are also available to suit bespoke laboratory requirements , with product R & D ongoing to achieve even lower vibration levels ( < 50 nm at the sample space ) .
Versatile product design is further evidenced in ICEoxford ’ s @ @ @ @ @ @ @ DRY ICE 1.5K 100 mm system to switch between static and dynamic exchange-gas mode for sample cooling .
Essentially , dynamic mode yields higher cooling powers , and in turn faster cool-down , after the sample probe is loaded into the cryostat at room temperature .
After this initial cooling , however , most users want the sample to be in a more stable vacuum or low-pressure , static-gas environment for their experiments , swapping from dynamic to static mode once the sample approaches target temperature .
Cooling aside , high-field superconducting magnets @ @ @ @ @ @ @ of the DRY ICE 1.5K 100 mm system , with ICEoxford offering a range of solenoid , split-pair and vector-rotate magnets up to 18 T field strength .
While studies of magnetic properties at ultralow temperatures are a given , many scientists also want to carry out simultaneous optical investigations of their materials – not so easy if the sample is sat within the large coil of a solenoid magnet .
In this case , one option is to load the sample into the bore of a split-pair magnet .
“ The DRY @ @ @ @ @ @ @ number of optical windows to allow , for example , laser spectroscopy experiments in transmission or reflection mode , ” explains Kelly .
The use of two- or three-way vector-rotate magnets provides further flexibility , with the latter able to generate a magnetic field in three discrete directions .
In this way , it is possible to keep the sample stationary while the magnetic field is varied around it – a key feature when studying a specific plane within a crystal lattice or if the heat generated by sample rotation is a source @ @ @ @ @ @ @ .
One other notable feature of the DRY ICE portfolio is the high degree of automation , with LabVIEW-based software used to control and monitor temperature in the DRY ICE 1.5K 100 mm system .
“ This has been developed with the customer in mind , ” concludes Kelly , “ to reduce the set-up and turnaround time of the system while increasing laboratory productivity.
” What ’ s more , it ’ s possible to add features to the software such as integrated control for the superconducting magnet as well as automating @ @ @ @ @ @ @ of the DRY ICE 1.5K cryostat are also available in configurations with 30 , 50 or 70 mm diameter sample space .

ICEoxford’s emphasis on versatile product design, rapid cool-down and a high degree of automation eases the path to ultralow temperatures
Cool customers: the ICEoxford engineering team works closely with clients to fully understand their requirements, tailoring product designs versus custom specifications. (Courtesy: ICEoxford)
ICEoxford, as the name suggests, is in the business of keeping things cold – ultracold to be precise. As such, the UK-based designer and manufacturer of specialist cryogenic systems supports fundamental and applied research efforts across a diverse customer base – from neutron and X-ray beamline scientists to quantum computing start-ups; from scanning-probe microscopy specialists to physicists studying the fundamental properties of high-temperature superconductors. “Generally, our customers want to get cold, get cold as quickly as possible, plus many want the option of studying their samples within a magnetic field,” explains Paul Kelly, Chief Technical Officer at ICEoxford.
With those requirements in mind, Kelly and his colleagues in Oxfordshire have pioneered the DRY ICE 1.5K 100 mm, a closed-loop cryostat that enables users to carry out experiments in the temperature range from 1.3 K to 325 K while ensuring tight tolerance on temperature stability (±10 mK below 10 K), fast cool-down times (<30 min to 1.4 K) and minimal vibration in the sample space (as little as ±100 nm). There’s also the option to add 3He and dilution-fridge inserts to achieve even lower temperatures (300 mK and 15 mK respectively).
Kelly, for his part, is keen to emphasize the win-win of a 100 mm diameter sample space matched with the cryostat’s high-cooling-power capability (>30 mW at 1.75 K). “This is the largest available sample space and highest cooling power on the market for a variable-temperature-insert [VTI] cryostat,” he claims. Equally significant is the fast-track cool-down cycle – and particularly so for scientists allocated time on the beamlines of big-science facilities like the ISIS Neutron and Muon Source or the Diamond Light Source (both also in Oxfordshire).
“Beam time is expensive and scientific users only get a fixed slot to complete their experiments – typically just a few days,” adds Kelly. Smaller laboratories also benefit, with the rapid cool-down translating into enhanced productivity versus research output (e.g. fast sample pre-testing in the cryogenic systems of quantum computers).
Good vibrations
Given the varied, often unique, requirements of ICEoxford’s end-users, the vendor sets a high bar for its design, engineering and manufacturing teams. Their task, says Kelly, is to bring a versatility of approach to all customer relationships, with a relentless focus on delivering the best system to do the job. “We work closely with the customer to fully understand their requirements and will tailor the product design to meet their exact specifications,” he notes.
Paul Kelly: “This is the largest available sample space and highest cooling power on the market for a VTI cryostat.” (Courtesy: ICEoxford)
The DRY ICE 1.5K 100 mm provides a case study in versatility, not least in terms of its vibration performance. The system can utilize two types of cryocooler: a Gifford-McMahon (GM) set-up (which relies on a mobile piston for compression and expansion of the helium fluid in the cold-head) or pulse-tube refrigerator (PTR) technology (with no moving parts in the low-temperature region). “Most users don’t see vibration as a show-stopper,” says Kelly, “but those who do are likely to choose PTR cooling, as the vibration is approaching an order of magnitude lower than GM.”
Further damping comes with the use of so-called “ICE sock” technology, a common method of vibration isolation across a range of ICEoxford products. “Put simply,” explains Kelly, “we build a container called a sock to surround the cryocooler. We then load the cooler into the sock and hold it away from any mechanical parts on a bellows.” A range of anti-vibration frames are also available to suit bespoke laboratory requirements, with product R&D ongoing to achieve even lower vibration levels (<50 nm at the sample space).
Versatile product design is further evidenced in ICEoxford’s patented Dual-Cool technology, which enables the DRY ICE 1.5K 100 mm system to switch between static and dynamic exchange-gas mode for sample cooling. Essentially, dynamic mode yields higher cooling powers, and in turn faster cool-down, after the sample probe is loaded into the cryostat at room temperature. After this initial cooling, however, most users want the sample to be in a more stable vacuum or low-pressure, static-gas environment for their experiments, swapping from dynamic to static mode once the sample approaches target temperature.
Magnetic attractions
Cooling aside, high-field superconducting magnets are designed to be an integral part of the DRY ICE 1.5K 100 mm system, with ICEoxford offering a range of solenoid, split-pair and vector-rotate magnets up to 18 T field strength. While studies of magnetic properties at ultralow temperatures are a given, many scientists also want to carry out simultaneous optical investigations of their materials – not so easy if the sample is sat within the large coil of a solenoid magnet.
In this case, one option is to load the sample into the bore of a split-pair magnet. “The DRY ICE system can be designed with a number of optical windows to allow, for example, laser spectroscopy experiments in transmission or reflection mode,” explains Kelly. The use of two- or three-way vector-rotate magnets provides further flexibility, with the latter able to generate a magnetic field in three discrete directions. In this way, it is possible to keep the sample stationary while the magnetic field is varied around it – a key feature when studying a specific plane within a crystal lattice or if the heat generated by sample rotation is a source of interference for small-scale electrical conductivity measurements.
One other notable feature of the DRY ICE portfolio is the high degree of automation, with LabVIEW-based software used to control and monitor temperature in the DRY ICE 1.5K 100 mm system. “This has been developed with the customer in mind,” concludes Kelly, “to reduce the set-up and turnaround time of the system while increasing laboratory productivity.” What’s more, it’s possible to add features to the software such as integrated control for the superconducting magnet as well as automating the top-load and probe cool-down.
Variants of the DRY ICE 1.5K cryostat are also available in configurations with 30, 50 or 70 mm diameter sample space.