physicsworld--2020-09-09--Has the COVID-19 lockdown changed Earth’s climate? - Physics World

COVID-19 has changed the world .
The pandemic has caused devastation , pain and loss , with no corner of the globe untouched .
But for some scientists the unprecedented disruption has also brought about a previously unimaginable opportunity .
The dramatic fall in air pollution that accompanied countries going into lockdown has provided a unique natural experiment , enabling scientists to probe some of the long-standing mysteries surrounding cloud formation .
In doing so , they have gained a better understanding of the complicated interactions between air pollution , weather and climate .
Stringent lockdown measures were first introduced @ @ @ @ @ @ @ was initially identified – on 23 January 2020 , and quickly rippled out across the rest of the country to combat the spread of the SARS-CoV-2 virus .
With public transport shut down , schools , universities and workplaces closed , and people confined to their homes , the streets became silent and air pollution plummeted .
Satellite data revealed , for example , that nitrogen dioxide had fallen by as much as 70 % ( figure 1 ) across eastern China , with some locations – including Wuhan – seeing drops of @ @ @ @ @ @ @ the virus swept around the world and other countries imposed their own versions of lockdown , the atmosphere responded , with smog being replaced by blue skies in New Delhi , the Himalayan mountain chain becoming visible from parts of northern India for the first time in 30 years , and city skylines being brought into sharp relief in Jakarta , Los Angeles , Paris and beyond .
However , cleaner air doesn ’ t necessarily result in wall-to-wall blue skies .
Just as a small amount of sugar or salt can make @ @ @ @ @ @ @ small changes in the composition of the atmosphere can trigger a chain reaction of interesting atmospheric effects : concocting new chemicals , making or breaking up clouds , and potentially changing the weather at the surface .
But teasing out those changes , against the background of natural climate variability , is difficult .
“ The most direct effect of reduced particle pollution on the weather will be on increasing the sunlight that can warm the surface , rather than being absorbed higher up in the atmosphere or reflected back to space , @ @ @ @ @ @ @ scientist at the University of Reading in the UK .
Earlier this year Allan and his colleagues showed that changes in air quality in recent decades have noticeably increased the amount of sunlight reaching the Earth ’ s surface ( Nature Geoscience 13 110 ) .
Their analysis of solar radiation measurements from the last 40 years revealed that grimy skies over Europe through the 1980s blocked sunlight and made it dimmer at ground level .
But the implementation of air-pollution regulations from the late-1980s had a significant brightening effect across Europe .
@ @ @ @ @ @ @ had to wait until around 2005 for its atmospheric clean-up and the accompanying brighter skies .
Cleaner skies have also been shown to impact atmospheric circulation patterns and extreme weather .
Last February Yuan Wang , a climate scientist at the California Institute of Technology in the US , and colleagues demonstrated that the reduction in air pollution across Europe since the 1970s has altered the strength and location of high-altitude winds , shifting the jet stream further to the north during winter ( Nature Climate Change 10 225 ) .
This movement @ @ @ @ @ @ @ events over northern Eurasia .
But what about over a shorter time period ?
What can we learn from the dramatic reduction in air pollution associated with COVID-19 lockdowns ?
“ Large-scale reductions in pollution due to COVID-19 will alter the heating patterns across the globe , particularly in south Asia , Europe and North America , and it is plausible that this will influence weather systems , ” says Allan .
“ But isolating this effect from the chaotic natural fluctuations in weather may be impossible.
” Cleaner air brought more cloud @ @ @ @ @ @ @ scientist at the IBS Center for Climate Physics in Busan , South Korea , agrees that in most locations the signal will be lost among the climate noise .
However , in early February he realized that the massive drop in air pollution accompanying lockdown over eastern China was likely to be large enough to trigger changes that rose above the noise , and since then he and his team have been working flat out to decipher the story that they tell .
“ We saw the massive drop in anthropogenic aerosols over @ @ @ @ @ @ @ cloud-condensation nuclei would result in fewer clouds , ” says Timmermann .
But his team was in for an interesting surprise .
To tease apart natural climate variability from the impact of lockdown , Timmermann and his team ran 40 simulations on their supercomputer using a model developed by the US National Center for Atmospheric Research .
Known as the Community Earth System Model , it is a coupled global climate model – meaning it links the ocean and atmosphere – that can simulate Earth ’ s past , present and future climate @ @ @ @ @ @ @ with atmospheric and oceanic conditions similar to those observed during January 2020 and modelled the following 12 months , with half the models simulating the climate conditions we ’ d expect in an ordinary year and the other half simulating the climate conditions with the coronavirus lockdown in place .
To represent these two scenarios , 20 simulations used average levels of air pollution for February based on the last few years ( but not including February 2020 ) , while the other 20 were spiked with a 65 % drop in aerosol @ @ @ @ @ @ @ of lockdown .
“ To our great surprise the simulations with reduced aerosols produced a significant increase in low cloud coverage and relative humidity over the region , ” says Timmermann , whose findings are now in review ( EarthArXiv 10.31223/osf.io/z5dm8 ) .
The lockdown-spiked simulations produced a good match with the actual conditions seen on the ground , which did feature a distinct rise in low cloud cover .
“ We still have a lot to learn about how aerosols control clouds , so this was a really exciting result , ” @ @ @ @ @ @ @ the reduction in the number of aerosols resulted in fewer cloud-condensation nuclei .
However , this enabled the remaining cloud-condensation nuclei to collect more moisture and form bigger droplets that didn ’ t evaporate as easily , helping the low clouds to stabilize and be longer-lived .
The time of year and prevailing weather conditions will also have played a role , and Timmermann is quick to point out that lockdown conditions at other times of year and under other weather scenarios would likely produce very different results .
Of course it is @ @ @ @ @ @ @ over north-eastern China during February 2020 was actually triggered by the improved air quality , and some scientists are cautious of reading too much into Timmermann ’ s findings .
“ It ’ s an interesting study but we have to be careful because meteorology can be anomalous for reasons other than changes in emissions , ” says Nicolas Bellouin , a climate scientist also at the University of Reading , although not part of the same project as Allan in this instance .
Indeed , another study published in June by Wang @ @ @ @ @ @ @ been more complex interactions at play over some regions of north-eastern China ( Science 10.1126/science.abb7431 ) .
The team ran atmospheric chemistry and meteorology simulations using air-pollution data from eastern China gathered between 23 January and 13 February this year – the most stringent period of lockdown in China .
“ We intuitively expected that the reduction in nitrogen dioxide and sulphur dioxide would result in fewer aerosols and therefore less haze , ” says Wang .
Observations from the megacities of Shanghai , Wuhan and Guangzhou appear to support this intuition .
@ @ @ @ @ @ @ surprise , the northern portion of their study area showed the exact opposite , with Beijing and surrounds experiencing severe choking haze .
In Beijing itself , the concentration of fine dust particles ( particulate matter with a diameter less than 2.5 μm , known as PM ) reached up to 200 μg/m3 – nearly 20 % more than normal for this time of year and way above the World Health Organization ’ s guideline daily value of 25 μg/m3 .
When Wang and his colleagues modelled the chemistry and meteorology , they @ @ @ @ @ @ @ emissions from factories during lockdown did not actually alleviate air pollution in Beijing and its surrounding area .
In this case , the high humidity and reduction in nitrogen oxides actually promoted the formation of another pollutant created by a secondary chemical reaction : ground-level ozone .
That ’ s because under ordinary conditions , nitrogen oxide helps to keep a lid on ozone levels by reacting with it and breaking it down into nitrogen dioxide and oxygen .
But with less nitrogen oxide around , ground-level ozone was able to persist for @ @ @ @ @ @ @ increasing by over one third in Wuhan for example ( Science of the Total Environment 735 139542 ) .
( In less industrialized areas the effect is muted because the fall in nitrogen oxides is not as great . )
Helping to speed this reaction along even faster were the volatile organic compounds that continued to spew out unabated from petrochemical facilities and oil refineries .
“ These secondary reactions have been discussed previously , but the new findings show that the reactions are more efficient than we ’ d previously realized , @ @ @ @ @ @ @ that Timmermann and his colleagues ’ proposed cloud-formation mechanism is a plausible feedback process , but in this case we don ’ t think it was the main driver of the ground-level haze.
” In recent years cities like Beijing have been using short-term emissions controls such as alternate-day driving rules and factory closures to prevent the formation of severe haze .
This appeared to be effective during the Olympic games in summer 2008 , and for the Asia-Pacific Economic Cooperation in November 2014 .
But the new research suggests that these air-quality @ @ @ @ @ @ @ down to good luck with the weather conditions at the time .
“ In both cases the near-surface humidity was not as high as it was during lockdown this year , ” says Wang .
Ironically , only cutting traffic could actually make things worse .
“ Our model simulations show that all sources of air pollution must be considered and that reducing volatile organic compounds is important too , because this helps to limit the secondary chemical reactions , ” he continues .
So what about elsewhere in the world ?
What @ @ @ @ @ @ @ India , Australia and South America entered lockdown and saw their air pollution plunge ?
Despite the hyperbole in the media , the drop in air pollution in other parts of the world wasn ’ t anywhere near as large as that seen in eastern China .
For example , instead of the 70 % drop in nitrogen dioxide levels observed there , satellite measurements show these fell by only 20–38 % over western Europe and the US compared with the same time in 2019 .
It ’ s an impressive drop , @ @ @ @ @ @ @ a measurable effect on the weather or climate .
Still , that doesn ’ t mean it isn ’ t worth looking into .
Towards the end of March India entered strict lockdown , with everything except essential services shut and 1.3 billion people told to stay home for 21 days .
As factories closed and animals reclaimed the streets , some areas showed hefty drops in air pollution , which if sustained for long enough might just influence climate .
Research under review ( Atmos .
Chem .
Phys .
Discuss .
@ @ @ @ @ @ @ out by climate scientist Laura Wilcox from the University of Reading and colleagues ( not including Allan and Bellouin in this instance ) , indicates that reductions in Asian air pollution sustained over a number of years would result in more intense tropical monsoon rains .
That ’ s because a thinner layer of haze over India would reflect less heat back into space .
This would cause temperatures over land to rise , increasing the contrast in temperature between oceans and land , and driving a faster and more intense water cycle @ @ @ @ @ @ @ with lockdown is likely to be more fleeting in nature , but there is still a small chance that it may influence climate over the country .
“ I ’ ve been watching India closely , ” says Wilcox .
“ We would typically expect to see summer monsoon onset during June , and would usually see both very hot temperatures and high aerosol levels ahead of it.
” In 2020 it is thought the drop in air pollution over northern India may help to drive a more intense monsoon .
Wilcox and @ @ @ @ @ @ @ measurements , and comparing them with previous years to determine if this is the case .
Initial indications suggest that the monsoon is weaker than average this year , but with some unusually intense convection events , bringing very heavy rains in July and severe floods to north-east India , Bangladesh , Bhutan , Myanmar and Nepal , killing hundreds of people and displacing as many as 4 million from their homes .
But it will take some time to work out whether the intense rains were linked to the drop in air @ @ @ @ @ @ @ quirk of the climate this year .
As well as understanding the impact that air pollution has on climate , atmospheric chemists have been using lockdown as an opportunity to better understand the sources of air pollution and the distances that pollution can travel .
In Europe , where lockdowns saw air-pollution patterns echo those observed in China , there were significant drops in nitrogen dioxide , but disappointingly small reductions ( or even increases ) in particulate pollution .
“ There has been quite a bit learnt about PM [ small particulate @ @ @ @ @ @ @ it is secondary in nature , and that simply reducing transport volumes doesn ’ t have a huge impact on particulates , ” says Alastair Lewis , an atmospheric chemist at the UK ’ s National Centre for Atmospheric Science .
“ The assumption is that the key contributing sources to secondary particulates , like ammonia from agriculture and volatile organic compounds from solvents , will have been emitted largely as normal , ” he adds .
If the changes associated with the COVID-19 pandemic lockdown have taught us anything it is how @ @ @ @ @ @ @ Earth ’ s atmosphere are , and how intimately meteorology and atmospheric chemistry are linked .
It ’ s clear that reducing air pollution can have unintended negative consequences , including changed weather patterns and a surge in secondary pollutants .
For cities wanting to keep a lid on localized air pollution , and prevent dangerous short-term spikes , the lockdown findings demonstrate that quick fixes aren ’ t always possible .
Instead , the best way of tackling air pollution in cities is to reduce pollution from all the different sources , @ @ @ @ @ @ @ bring its own problems .
Earlier this year Wilcox and her colleagues published research showing that rapid cuts in air pollution are likely to accelerate climate change in the future ( Environ .
Res .
Lett .
15 034013 ) .
In the most extreme scenarios with rapid increases in air quality , their results suggest the hottest day of the year may be up to 4 °C hotter by 2050 , with around one third of that increase due to cleaner skies .
Nonetheless , the cost of failing to cut air @ @ @ @ @ @ @ to emit greenhouse gases into the atmosphere at the current rate will drive far larger and more sustained temperature rises , ” explains Allan .
“ That , along with changes in the global water cycle , will cause serious impacts for our societies and the ecosystems upon which we depend .
”

Physics World. Members of the Institute of Physics can enjoy the full issue Taken from the September 2020 issue of. Members of the Institute of Physics can enjoy the full issue via the Physics World app
The lockdown measures imposed by many nations due to the COVID-19 pandemic have led to air pollution falling dramatically, thereby offering scientists a rare opportunity to study its links with climate and weather. But as Kate Ravilious discovers, it’s a complicated connection
Shrouded cities Smog has reduced over many metropolitan areas, including Shanghai, thanks to lockdown restrictions, but in other places the smog is worse than ever. (Courtesy: iStock/fazon1)
COVID-19 has changed the world. The pandemic has caused devastation, pain and loss, with no corner of the globe untouched. But for some scientists the unprecedented disruption has also brought about a previously unimaginable opportunity. The dramatic fall in air pollution that accompanied countries going into lockdown has provided a unique natural experiment, enabling scientists to probe some of the long-standing mysteries surrounding cloud formation. In doing so, they have gained a better understanding of the complicated interactions between air pollution, weather and climate.
Stringent lockdown measures were first introduced in Wuhan, China – where COVID-19 was initially identified – on 23 January 2020, and quickly rippled out across the rest of the country to combat the spread of the SARS-CoV-2 virus. With public transport shut down, schools, universities and workplaces closed, and people confined to their homes, the streets became silent and air pollution plummeted. Satellite data revealed, for example, that nitrogen dioxide had fallen by as much as 70% (figure 1) across eastern China, with some locations – including Wuhan – seeing drops of up to 93%. And as the virus swept around the world and other countries imposed their own versions of lockdown, the atmosphere responded, with smog being replaced by blue skies in New Delhi, the Himalayan mountain chain becoming visible from parts of northern India for the first time in 30 years, and city skylines being brought into sharp relief in Jakarta, Los Angeles, Paris and beyond.
However, cleaner air doesn’t necessarily result in wall-to-wall blue skies. Just as a small amount of sugar or salt can make a cake taste very different, so small changes in the composition of the atmosphere can trigger a chain reaction of interesting atmospheric effects: concocting new chemicals, making or breaking up clouds, and potentially changing the weather at the surface. But teasing out those changes, against the background of natural climate variability, is difficult.
1 What a difference a month makes Airborne nitrogen dioxide (NO 2 ) – which is primarily emitted by industry and traffic – plummeted over China after Wuhan went into lockdown on 23 January and the surrounding regions quickly followed. Over eastern China in particular, levels dropped by 70%. (Courtesy: NASA)
Keeping a lid on global warming
“The most direct effect of reduced particle pollution on the weather will be on increasing the sunlight that can warm the surface, rather than being absorbed higher up in the atmosphere or reflected back to space,” says Richard Allan, a climate scientist at the University of Reading in the UK. Earlier this year Allan and his colleagues showed that changes in air quality in recent decades have noticeably increased the amount of sunlight reaching the Earth’s surface (Nature Geoscience 13 110). Their analysis of solar radiation measurements from the last 40 years revealed that grimy skies over Europe through the 1980s blocked sunlight and made it dimmer at ground level. But the implementation of air-pollution regulations from the late-1980s had a significant brightening effect across Europe. China has followed a similar path but had to wait until around 2005 for its atmospheric clean-up and the accompanying brighter skies.
Cleaner skies have also been shown to impact atmospheric circulation patterns and extreme weather. Last February Yuan Wang, a climate scientist at the California Institute of Technology in the US, and colleagues demonstrated that the reduction in air pollution across Europe since the 1970s has altered the strength and location of high-altitude winds, shifting the jet stream further to the north during winter (Nature Climate Change 10 225). This movement has lessened the likelihood of extreme cold events over northern Eurasia.
But what about over a shorter time period? What can we learn from the dramatic reduction in air pollution associated with COVID-19 lockdowns? “Large-scale reductions in pollution due to COVID-19 will alter the heating patterns across the globe, particularly in south Asia, Europe and North America, and it is plausible that this will influence weather systems,” says Allan. “But isolating this effect from the chaotic natural fluctuations in weather may be impossible.”
Cleaner air brought more cloud for some
Axel Timmermann, a climate scientist at the IBS Center for Climate Physics in Busan, South Korea, agrees that in most locations the signal will be lost among the climate noise. However, in early February he realized that the massive drop in air pollution accompanying lockdown over eastern China was likely to be large enough to trigger changes that rose above the noise, and since then he and his team have been working flat out to decipher the story that they tell.
“We saw the massive drop in anthropogenic aerosols over eastern China and naively reasoned that fewer cloud-condensation nuclei would result in fewer clouds,” says Timmermann. But his team was in for an interesting surprise.
To tease apart natural climate variability from the impact of lockdown, Timmermann and his team ran 40 simulations on their supercomputer using a model developed by the US National Center for Atmospheric Research. Known as the Community Earth System Model, it is a coupled global climate model – meaning it links the ocean and atmosphere – that can simulate Earth’s past, present and future climate state. Each of the simulations started with atmospheric and oceanic conditions similar to those observed during January 2020 and modelled the following 12 months, with half the models simulating the climate conditions we’d expect in an ordinary year and the other half simulating the climate conditions with the coronavirus lockdown in place. To represent these two scenarios, 20 simulations used average levels of air pollution for February based on the last few years (but not including February 2020), while the other 20 were spiked with a 65% drop in aerosol emissions in February to mimic the impact of lockdown.
To our great surprise the simulations with reduced aerosols produced a significant increase in low cloud coverage and relative humidity over the region Axel Timmermann
“To our great surprise the simulations with reduced aerosols produced a significant increase in low cloud coverage and relative humidity over the region,” says Timmermann, whose findings are now in review (EarthArXiv 10.31223/osf.io/z5dm8). The lockdown-spiked simulations produced a good match with the actual conditions seen on the ground, which did feature a distinct rise in low cloud cover.
“We still have a lot to learn about how aerosols control clouds, so this was a really exciting result,” says Timmermann. The simulations suggest that the reduction in the number of aerosols resulted in fewer cloud-condensation nuclei. However, this enabled the remaining cloud-condensation nuclei to collect more moisture and form bigger droplets that didn’t evaporate as easily, helping the low clouds to stabilize and be longer-lived. The time of year and prevailing weather conditions will also have played a role, and Timmermann is quick to point out that lockdown conditions at other times of year and under other weather scenarios would likely produce very different results.
Of course it is impossible to say if the low cloud over north-eastern China during February 2020 was actually triggered by the improved air quality, and some scientists are cautious of reading too much into Timmermann’s findings. “It’s an interesting study but we have to be careful because meteorology can be anomalous for reasons other than changes in emissions,” says Nicolas Bellouin, a climate scientist also at the University of Reading, although not part of the same project as Allan in this instance.
Indeed, another study published in June by Wang and colleagues suggests that there may have been more complex interactions at play over some regions of north-eastern China (Science 10.1126/science.abb7431). The team ran atmospheric chemistry and meteorology simulations using air-pollution data from eastern China gathered between 23 January and 13 February this year – the most stringent period of lockdown in China. “We intuitively expected that the reduction in nitrogen dioxide and sulphur dioxide would result in fewer aerosols and therefore less haze,” says Wang.
Observations from the megacities of Shanghai, Wuhan and Guangzhou appear to support this intuition. But to Wang and his colleagues’ surprise, the northern portion of their study area showed the exact opposite, with Beijing and surrounds experiencing severe choking haze. In Beijing itself, the concentration of fine dust particles (particulate matter with a diameter less than 2.5 μm, known as PM 2.5 ) reached up to 200 μg/m3 – nearly 20% more than normal for this time of year and way above the World Health Organization’s guideline daily value of 25 μg/m3.
When Wang and his colleagues modelled the chemistry and meteorology, they found that the reduction in traffic and emissions from factories during lockdown did not actually alleviate air pollution in Beijing and its surrounding area. In this case, the high humidity and reduction in nitrogen oxides actually promoted the formation of another pollutant created by a secondary chemical reaction: ground-level ozone. That’s because under ordinary conditions, nitrogen oxide helps to keep a lid on ozone levels by reacting with it and breaking it down into nitrogen dioxide and oxygen. But with less nitrogen oxide around, ground-level ozone was able to persist for longer than usual, resulting in concentrations increasing by over one third in Wuhan for example (Science of the Total Environment 735 139542). (In less industrialized areas the effect is muted because the fall in nitrogen oxides is not as great.) Helping to speed this reaction along even faster were the volatile organic compounds that continued to spew out unabated from petrochemical facilities and oil refineries. “These secondary reactions have been discussed previously, but the new findings show that the reactions are more efficient than we’d previously realized,” says Wang. “We think that Timmermann and his colleagues’ proposed cloud-formation mechanism is a plausible feedback process, but in this case we don’t think it was the main driver of the ground-level haze.”
In recent years cities like Beijing have been using short-term emissions controls such as alternate-day driving rules and factory closures to prevent the formation of severe haze. This appeared to be effective during the Olympic games in summer 2008, and for the Asia-Pacific Economic Cooperation in November 2014. But the new research suggests that these air-quality success stories in Beijing may be more down to good luck with the weather conditions at the time. “In both cases the near-surface humidity was not as high as it was during lockdown this year,” says Wang. Ironically, only cutting traffic could actually make things worse. “Our model simulations show that all sources of air pollution must be considered and that reducing volatile organic compounds is important too, because this helps to limit the secondary chemical reactions,” he continues.
Empty skies Grounded Reduced air traffic in response to COVID-19 provides a unique opportunity to study the impact of aviation on cloud formation. (Courtesy: Shutterstock/Tim Roberts Photography) Nicolas Bellouin at the University of Reading, UK, thinks that it might be possible to detect a change in cloud cover by focusing on a very specific aspect of lockdown: the extreme disruption to air traffic. “Because air traffic follows well defined corridors, particularly between Europe and the US, and the US and Asia, we can look for changes in cloud properties along these corridors,” he says. Aviation impacts the composition of the atmosphere via the trails of condensed water they leave behind them (contrails) and the particulates emitted from jet engines. “We’re not really sure how effective those soot particles are at nucleating ice,” says Bellouin, “but our hypothesis is that with fewer particulates being emitted there will be fewer cloud-condensation nuclei and we’d expect to see fewer or thinner cirrus clouds.” Together with colleagues, Bellouin is gathering satellite data with the aim of comparing busy air traffic routes during lockdown with their equivalent from the past. “In order to try and rule out changes due to anomalous weather conditions we search for days from the past that have similar meteorology to the lockdown days,” explains Bellouin. “This is a time-consuming and complex process.” The team hopes to have some results later in the year.
Did lockdown alter India’s monsoon?
So what about elsewhere in the world? What happened as Europe, the US, India, Australia and South America entered lockdown and saw their air pollution plunge? Despite the hyperbole in the media, the drop in air pollution in other parts of the world wasn’t anywhere near as large as that seen in eastern China. For example, instead of the 70% drop in nitrogen dioxide levels observed there, satellite measurements show these fell by only 20–38% over western Europe and the US compared with the same time in 2019. It’s an impressive drop, but probably not big enough to have a measurable effect on the weather or climate.
2 Aerosol emissions fall over Europe and Asia Maps showing the fractional change of the model anthropogenic aerosol emissions during the months of lockdown relative to the 2016–2019 baseline period. The drop in air pollution over western Europe and India was far more muted than the 70% fall seen over eastern China. (Courtesy: Axel Timmermann)
Still, that doesn’t mean it isn’t worth looking into. Towards the end of March India entered strict lockdown, with everything except essential services shut and 1.3 billion people told to stay home for 21 days. As factories closed and animals reclaimed the streets, some areas showed hefty drops in air pollution, which if sustained for long enough might just influence climate. Research under review (Atmos. Chem. Phys. Discuss. 10.5194/acp-2019-1188, in review), carried out by climate scientist Laura Wilcox from the University of Reading and colleagues (not including Allan and Bellouin in this instance), indicates that reductions in Asian air pollution sustained over a number of years would result in more intense tropical monsoon rains. That’s because a thinner layer of haze over India would reflect less heat back into space. This would cause temperatures over land to rise, increasing the contrast in temperature between oceans and land, and driving a faster and more intense water cycle.
The drop in air pollution associated with lockdown is likely to be more fleeting in nature, but there is still a small chance that it may influence climate over the country. “I’ve been watching India closely,” says Wilcox. “We would typically expect to see summer monsoon onset during June, and would usually see both very hot temperatures and high aerosol levels ahead of it.” In 2020 it is thought the drop in air pollution over northern India may help to drive a more intense monsoon. Wilcox and her colleagues are busy gathering and analysing measurements, and comparing them with previous years to determine if this is the case. Initial indications suggest that the monsoon is weaker than average this year, but with some unusually intense convection events, bringing very heavy rains in July and severe floods to north-east India, Bangladesh, Bhutan, Myanmar and Nepal, killing hundreds of people and displacing as many as 4 million from their homes. But it will take some time to work out whether the intense rains were linked to the drop in air pollution, or were simply a random quirk of the climate this year.
Cutting air pollution ain’t simple
As well as understanding the impact that air pollution has on climate, atmospheric chemists have been using lockdown as an opportunity to better understand the sources of air pollution and the distances that pollution can travel. In Europe, where lockdowns saw air-pollution patterns echo those observed in China, there were significant drops in nitrogen dioxide, but disappointingly small reductions (or even increases) in particulate pollution. “There has been quite a bit learnt about PM 2.5 [small particulate pollution], reinforcing that much of it is secondary in nature, and that simply reducing transport volumes doesn’t have a huge impact on particulates,” says Alastair Lewis, an atmospheric chemist at the UK’s National Centre for Atmospheric Science. “The assumption is that the key contributing sources to secondary particulates, like ammonia from agriculture and volatile organic compounds from solvents, will have been emitted largely as normal,” he adds.
If the changes associated with the COVID-19 pandemic lockdown have taught us anything it is how very complex the reactions that occur in Earth’s atmosphere are, and how intimately meteorology and atmospheric chemistry are linked. It’s clear that reducing air pollution can have unintended negative consequences, including changed weather patterns and a surge in secondary pollutants. For cities wanting to keep a lid on localized air pollution, and prevent dangerous short-term spikes, the lockdown findings demonstrate that quick fixes aren’t always possible. Instead, the best way of tackling air pollution in cities is to reduce pollution from all the different sources, but even this seemingly benign action could bring its own problems.
Earlier this year Wilcox and her colleagues published research showing that rapid cuts in air pollution are likely to accelerate climate change in the future (Environ. Res. Lett. 15 034013). In the most extreme scenarios with rapid increases in air quality, their results suggest the hottest day of the year may be up to 4 °C hotter by 2050, with around one third of that increase due to cleaner skies.
Nonetheless, the cost of failing to cut air pollution is far higher. “Continuing to emit greenhouse gases into the atmosphere at the current rate will drive far larger and more sustained temperature rises,” explains Allan. “That, along with changes in the global water cycle, will cause serious impacts for our societies and the ecosystems upon which we depend.”


physicsworld--2020-09-09--Silk hard drive stores optical data - Physics World

Researchers in the US and China have made the first-ever silk hard drive using a technique called tip-enhanced near-field infrared nanolithography ( TNINL ) .
The device , which can store digital data with a density of 64 GB per square inch , is robust in the face of harsh conditions such as heat , moisture , gamma radiation or high magnetic fields .
While a silk-based hard drive is unlikely to match the speed and storage capacity of state-of-the-art solid-state drives at the same cost , its unique set of features makes it promising for electronics that could be @ @ @ @ @ @ @ are routinely used to make devices with optical storage densities as high as several hundred GB per square inch .
However , it can be time-consuming to create small features with these methods , and it also requires costly and sophisticated fabrication procedures .
Another drawback is that diffraction limits the resolution of conventional optical lithography to around half the wavelength of the illuminating light – roughly hundreds of nanometres for visible light .
This makes further increases in storage density ( beyond current industry standards ) difficult to achieve .
An alternative @ @ @ @ @ @ @ microscopy ( s-SNOM ) offers a possible solution .
This technique gets around the diffraction limit because it depends on near-field light – that is , the component of light that “ wraps around ” surfaces – instead of the diffraction-prone far-field light ( which propagates away from the structures that scatter it ) .
Near-field light is already commonly used in nanoscience as a tool to fabricate , manipulate and characterize photosensitive structures .
For example , researchers use so-called “ evanescent ” light fields for nanolithography of polymeric materials , and @ @ @ @ @ @ @ when making optical nanodevices .
Researchers led by Tiger Tao of the Chinese Academy of Sciences in Shanghai , Mengkun Liu of Stony Brook University in New York and Wei Li of the University of Texas at Austin have now used a variation of s-SNOM to write and read information on a layer of silk protein .
To make their silk drives , the researchers took silk extracted from silkworm cocoons and spin-coated a thin film of it ( in the form of an aqueous solution ) onto either a gold or a @ @ @ @ @ @ @ patterns in this film using an s-SNOM equipped with a mid-infrared laser light source .
The frequency of the laser could be tuned between 1495 and 1790 cm-1 , which covers the wavelengths at which silk proteins absorb light .
By focusing the laser onto the sharp tip of an atomic force microscope placed near the silk surface , they were able to induce topological and/or phase changes in the silk film at roughly 30-nm length scales .
Information can be repeatedly written and erased With these induced changes spaced 100 nm apart @ @ @ @ @ @ @ capacity equivalent to around 64 GB per square inch , Liu says .
While the patterns thus created are robust to harsh conditions , the method nevertheless allows information to be repeatedly written onto and erased from the film .
The advantages of the technique are many , Liu tells Physics World .
Thin silk films are easy to spin-coat onto various substrates , including curved and soft materials .
Such films also offer two entirely different ways to read out the encoded data .
The first option is to use straightforward AFM @ @ @ @ @ @ @ are recognized as “ 1s ” while flat topographical features correspond to “ 0s ” .
The second , more innovative way is to use a laser readout technique that differs from conventional optical methods in that the spectroscopic information thus obtained is multi-coloured .
What is more , by varying the laser ’ s writing power , the researchers demonstrated that they could achieve so-called “ higher-dimensional ” or greyscale data storage , where individual data points take on values other than a binary zero or one .
Finally , Liu notes @ @ @ @ @ @ @ mixes and interfaces well with many biological systems , including biomarkers in blood .
The information in these biomarkers could therefore be encoded and stably stored in a silk-based hard drive .
Indeed , members of the team , who report their work in Nature Nanotechnology , now plan to integrate their silk drive with biological materials for bio-information storage applications .
“ We will be investigating body implantation in the near future as well , ” Liu says .

Heights and AFM topography of dots written with different frequencies and exposure times of the incident laser. Courtesy: M Liu
Researchers in the US and China have made the first silk hard drive using a technique called tip-enhanced near-field infrared nanolithography (TNINL). The device, which can store digital data with a density of 64 GB per square inch, is robust in the face of harsh conditions such as heat, moisture, gamma radiation or high magnetic fields. While a silk-based hard drive is unlikely to match the speed and storage capacity of state-of-the-art solid-state drives at the same cost, its unique set of features makes it promising for electronics that could be implanted in the body.
Lithography techniques are routinely used to make devices with optical storage densities as high as several hundred GB per square inch. However, it can be time-consuming to create small features with these methods, and it also requires costly and sophisticated fabrication procedures. Another drawback is that diffraction limits the resolution of conventional optical lithography to around half the wavelength of the illuminating light – roughly hundreds of nanometres for visible light. This makes further increases in storage density (beyond current industry standards) difficult to achieve.
Overcoming the diffraction limit with near-field light
An alternative technique known as scattering-type scanning near-field optical microscopy (s-SNOM) offers a possible solution. This technique gets around the diffraction limit because it depends on near-field light – that is, the component of light that “wraps around” surfaces – instead of the diffraction-prone far-field light (which propagates away from the structures that scatter it). Near-field light is already commonly used in nanoscience as a tool to fabricate, manipulate and characterize photosensitive structures. For example, researchers use so-called “evanescent” light fields for nanolithography of polymeric materials, and for processing nanoscale features in material surfaces when making optical nanodevices.
Researchers led by Tiger Tao of the Chinese Academy of Sciences in Shanghai, Mengkun Liu of Stony Brook University in New York and Wei Li of the University of Texas at Austin have now used a variation of s-SNOM to write and read information on a layer of silk protein.
To make their silk drives, the researchers took silk extracted from silkworm cocoons and spin-coated a thin film of it (in the form of an aqueous solution) onto either a gold or a silicon substrate. They then created nanoscopic patterns in this film using an s-SNOM equipped with a mid-infrared laser light source. The frequency of the laser could be tuned between 1495 and 1790 cm–1, which covers the wavelengths at which silk proteins absorb light. By focusing the laser onto the sharp tip of an atomic force microscope placed near the silk surface, they were able to induce topological and/or phase changes in the silk film at roughly 30-nm length scales.
Information can be repeatedly written and erased
With these induced changes spaced 100 nm apart, the team achieved a data storage capacity equivalent to around 64 GB per square inch, Liu says. While the patterns thus created are robust to harsh conditions, the method nevertheless allows information to be repeatedly written onto and erased from the film.
The advantages of the technique are many, Liu tells Physics World. Thin silk films are easy to spin-coat onto various substrates, including curved and soft materials. Such films also offer two entirely different ways to read out the encoded data. The first option is to use straightforward AFM “mapping” in which topographic protrusions are recognized as “1s” while flat topographical features correspond to “0s”. The second, more innovative way is to use a laser readout technique that differs from conventional optical methods in that the spectroscopic information thus obtained is multi-coloured. What is more, by varying the laser’s writing power, the researchers demonstrated that they could achieve so-called “higher-dimensional” or greyscale data storage, where individual data points take on values other than a binary zero or one.
Finally, Liu notes that silk is an organic material that mixes and interfaces well with many biological systems, including biomarkers in blood. The information in these biomarkers could therefore be encoded and stably stored in a silk-based hard drive. Indeed, members of the team, who report their work in Nature Nanotechnology, now plan to integrate their silk drive with biological materials for bio-information storage applications. “We will be investigating body implantation in the near future as well,” Liu says.


physicsworld--2020-09-10--Stable recordings enable ‘plug-and-play’ control of brain–computer interface - Physics World

Brain–computer interfaces ( BCIs ) offer the potential for people with severe motor disabilities to control external assistive devices with their mind .
Current BCI systems are limited , however , by the need for daily recalibration of the decoder that converts neural activity into control signals .
Researchers at the UC San Francisco Weill Institute for Neurosciences have now employed machine learning to help an individual with tetraplegia learn to control a computer cursor using their brain activity , without requiring extensive daily retraining .
To record neural activity , the team used a 128-channel electrocorticography ( ECoG ) @ @ @ @ @ @ @ ’ s surgically placed on the surface of the brain .
Already approved for seizure monitoring in epilepsy patients , ECoG arrays provide greater long-term stability than the pincushion-style arrays of sharp electrodes used in previous BCI studies , which are more sensitive but tend to move or lose signal over time .
“ The BCI field has made great progress in recent years , but because existing systems have had to be reset and recalibrated each day , they haven ’ t been able to tap into the brain ’ s natural @ @ @ @ @ @ @ Karunesh Ganguly .
“ It ’ s like asking someone to learn to ride a bike over and over again from scratch.
” The researchers developed a BCI algorithm that uses machine learning ( based on an adaptative Kalman filter ) to map the neural activity recorded by the ECoG electrodes to the user ’ s desired cursor movements .
Over a period of roughly six months ( two months after ECoG implantation ) , they conducted experiments to assess two approaches for adaptation of this decoder algorithm as the user learns control @ @ @ @ @ @ @ practice of resetting the algorithm each day .
Here , the participant imagined movements of his neck and right wrist while watching a cursor move across the screen , and the algorithm gradually updated itself to match the cursor ’ s movements to the generated brain activity .
This daily initialization , however , could require hours for the participant to master cursor control ; some days , he could not achieve control at all .
Next , the researchers examined an approach called long-term closed-loop decoder adaptation ( CLDA ) , in @ @ @ @ @ @ @ ’ s session are used for the current session , without resetting the algorithm each day .
They found that continued interplay between the participant ’ s brain signals and the algorithm resulted in continuous improvements in performance over many days .
When the team reset the BCI algorithm after several weeks of continuous learning , the participant rapidly re-established the same patterns of neural activity required to control the device – effectively retraining the algorithm to its former state .
“ Once the user has established an enduring memory of the solution @ @ @ @ @ @ @ s no need for resetting , ” says Ganguly .
“ The brain just rapidly convergences back to the same solution.
” The researchers next examined whether long-term CLDA could enable long-term stable performance without the need for retraining or recalibration – the so-called “ plug-and-play ” performance that could enable broader use of BCIs .
They found that once expertise was established , the participant could simply begin using the BCI each day .
His performance did not decline over 44 days without retraining , and he showed little performance decline after @ @ @ @ @ @ @ , the participant was also able to “ stack ” additional skills , such as clicking a virtual button , without impacting his ability to control the cursor .
To differentiate clicking from cursor control , the researchers trained a linear support vector machine ( SVM ) .
“ One of the main innovations was the rate at which the Kalman filter and SVM parameters were adapted across days in order to track user learning and neural plasticity , ” Ganguly notes .
Ganguly and colleagues conclude that by leveraging the stability of @ @ @ @ @ @ @ approach offers reliable , stable BCI control .
This stability may prove even more important for long-term control of more complex robotic systems such as artificial limbs – a key goal of the next phase of this research .
The team is now in the process of enrolling the next subject , says Ganguly .
“ We are also developing new approaches to increasing communication rates ; this involves more sophisticated algorithms and using a denoised decoding of neural activity .
And we are testing control of a six degrees-of-freedom robotic arm – @ @ @ @ @ @ @ physics engine , ” he tells Physics World .
The results are reported in Nature Biotechnology .

Senior author Karunesh Ganguly discusses electrocorticography brain recording data with student Stefan Lemke. (Courtesy: UCSF)
Brain–computer interfaces (BCIs) offer the potential for people with severe motor disabilities to control external assistive devices with their mind. Current BCI systems are limited, however, by the need for daily recalibration of the decoder that converts neural activity into control signals. Researchers at the UC San Francisco Weill Institute for Neurosciences have now employed machine learning to help an individual with tetraplegia learn to control a computer cursor using their brain activity, without requiring extensive daily retraining.
To record neural activity, the team used a 128-channel electrocorticography (ECoG) implant, a pad of electrodes that’s surgically placed on the surface of the brain. Already approved for seizure monitoring in epilepsy patients, ECoG arrays provide greater long-term stability than the pincushion-style arrays of sharp electrodes used in previous BCI studies, which are more sensitive but tend to move or lose signal over time.
“The BCI field has made great progress in recent years, but because existing systems have had to be reset and recalibrated each day, they haven’t been able to tap into the brain’s natural learning processes,” explains senior author Karunesh Ganguly. “It’s like asking someone to learn to ride a bike over and over again from scratch.”
The ECoG implant. (Courtesy: Noah Berger/UCSF)
The researchers developed a BCI algorithm that uses machine learning (based on an adaptative Kalman filter) to map the neural activity recorded by the ECoG electrodes to the user’s desired cursor movements. Over a period of roughly six months (two months after ECoG implantation), they conducted experiments to assess two approaches for adaptation of this decoder algorithm as the user learns control.
First, they tested the existing practice of resetting the algorithm each day. Here, the participant imagined movements of his neck and right wrist while watching a cursor move across the screen, and the algorithm gradually updated itself to match the cursor’s movements to the generated brain activity. This daily initialization, however, could require hours for the participant to master cursor control; some days, he could not achieve control at all.
Next, the researchers examined an approach called long-term closed-loop decoder adaptation (CLDA), in which decoder weights from the previous day’s session are used for the current session, without resetting the algorithm each day. They found that continued interplay between the participant’s brain signals and the algorithm resulted in continuous improvements in performance over many days.
When the team reset the BCI algorithm after several weeks of continuous learning, the participant rapidly re-established the same patterns of neural activity required to control the device – effectively retraining the algorithm to its former state. “Once the user has established an enduring memory of the solution for controlling the interface, there’s no need for resetting,” says Ganguly. “The brain just rapidly convergences back to the same solution.”
The researchers next examined whether long-term CLDA could enable long-term stable performance without the need for retraining or recalibration – the so-called “plug-and-play” performance that could enable broader use of BCIs. They found that once expertise was established, the participant could simply begin using the BCI each day. His performance did not decline over 44 days without retraining, and he showed little performance decline after days without practicing.
At this stage, the participant was also able to “stack” additional skills, such as clicking a virtual button, without impacting his ability to control the cursor. To differentiate clicking from cursor control, the researchers trained a linear support vector machine (SVM). “One of the main innovations was the rate at which the Kalman filter and SVM parameters were adapted across days in order to track user learning and neural plasticity,” Ganguly notes.
Ganguly and colleagues conclude that by leveraging the stability of ECoG interfaces and neural plasticity, this approach offers reliable, stable BCI control. This stability may prove even more important for long-term control of more complex robotic systems such as artificial limbs – a key goal of the next phase of this research.
The team is now in the process of enrolling the next subject, says Ganguly. “We are also developing new approaches to increasing communication rates; this involves more sophisticated algorithms and using a denoised decoding of neural activity. And we are testing control of a six degrees-of-freedom robotic arm – we currently have a simulation in a physics engine,” he tells Physics World.
The results are reported in Nature Biotechnology.


physicsworld--2020-09-10--How the Doomsday Clock ticks, dusting on the Moon, Proxima reflects on women in STEM - Physics World

For almost 75 years , the Doomsday Clock has monitored how close humankind is to global catastrophe .
With the clock now closer to midnight than ever before , the science writer Rachel Brazil talks to Physics World ’ s Matin Durrani about how the clock is set by the Bulletin of the Atomic Scientists and how physicists can engage in public debates about the challenges facing civilization .
Space travel is one challenge that humans have overcome , and we could soon embark on a second era of exploration that culminates in the colonization of the Moon .
Lunar @ @ @ @ @ @ @ nemesis of Moon dwellers because the stuff gets everywhere and can damage spacesuits and other essential technologies .
Xu Wang and Ben Farr of the Laboratory for Atmospheric and Space Physics at the University of Colorado Boulder join the podcast to explain how beams of electrons could help keep equipment dust free on the Moon .
The film Proxima looks at the themes of motherhood , separation , and sexism from the perspective of an astronaut who is preparing to spend a year on the International Space Station .
Physics World ’ s @ @ @ @ @ @ @ her impressions of the film and to chat about an interview we have done with the writer and director Alice Winocour .

For almost 75 years, the Doomsday Clock has monitored how close humankind is to global catastrophe. With the clock now closer to midnight than ever before, the science writer Rachel Brazil talks to Physics World’s Matin Durrani about how the clock is set by the Bulletin of the Atomic Scientists and how physicists can engage in public debates about the challenges facing civilization.
Space travel is one challenge that humans have overcome, and we could soon embark on a second era of exploration that culminates in the colonization of the Moon. Lunar dust, however, could be the nemesis of Moon dwellers because the stuff gets everywhere and can damage spacesuits and other essential technologies. Xu Wang and Ben Farr of the Laboratory for Atmospheric and Space Physics at the University of Colorado Boulder join the podcast to explain how beams of electrons could help keep equipment dust free on the Moon.
The film Proxima looks at the themes of motherhood, separation and sexism from the perspective of an astronaut who is preparing to spend a year on the International Space Station. Physics World’s Tushna Commissariat is on hand to give her impressions of the film and to chat about our interview with the film’s writer and director Alice Winocour.


physicsworld--2020-09-11--Opportunities and fundamental challenges for anion exchange membrane fuel cells - Physics World

In recent years , advances in alkaline exchange membrane fuel cells ( AEMFCs ) with anion exchange membrane ( AEM ) solid polymer electrolytes have gained traction due to their distinct , and potentially game-changing , advantages over proton exchange membrane fuel cells .
There has been growing excitement in the past 2–3 years , especially as AEMFCs have reached a stage in their development where state-of-the-art cells are reaching comparable power densities to proton exchange membrane fuel cells ( PEMFCs ) and are able to operate stably for more than 1000 hours .
However , AEMFCs still need to @ @ @ @ @ @ @ they are to be deployed in the field : • Water management in AEMFCs is more complex than PEMFCs and there is a tendency for significant water accumulation and flooding at the anode – sacrificing both performance and longevity .
• There is a need to reduce costs significantly below the PEMFCs and doing this will require completely PGM-free catalysts .
• Management of CO and mitigation of CO -related performance losses .
This presentation will begin with an introduction to how AEMFCs operate , their similarities and differences to PEMFCs .
Then @ @ @ @ @ @ @ shown along with an explanation for how these two were systematically improved over the past few years due to advances in materials as well as innovations in electrode design and reactor engineering .
Next , the three issues above – water management , PGM-free catalysts and CO management – will be discussed , with a focus on the fundamental thermodynamic , kinetic and transport barriers that remain .
Finally , an outlook on the future of the technology and important areas for research will be discussed .
William ( Bill ) Mustain is @ @ @ @ @ @ @ Engineering at the University of South Carolina ( USC ) .
In 2017 , he moved to USC from the Department of Chemical and Biomolecular Engineering at the University of Connecticut ( UConn ) where he was an Associate Professor and the United Technologies Corporation Professor of Engineering Innovation .
He joined UConn as an Assistant Professor in 2008 and was tenured and promoted to Associate Professor in 2013 .
Professor Mustain has worked in several areas related to electrochemical energy generation and storage including : high-capacity materials for lithium-ion batteries , catalysts @ @ @ @ @ @ @ anion exchange membrane fuel cells and electrolyzers , electrochemical synthesis of fuels , electrochemical control of biological systems , the purposeful use of carbonates in low-temperature electrochemical systems , and the electrochemical capture and utilization of CO .
He has been the PI or co-PI on approximately $ 10m of externally funded research projects .
He has published more than 100 peer-reviewed articles and three book chapters to date and has more than 100 invited and conference talks .
He has been the recipient of several awards including the 2009 Illinois Institute of @ @ @ @ @ @ @ Department of Energy Early Career Award ; 2014 Connecticut Quality Improvement Platinum Award ; 2014 Supramaniam Srinivasan Young Investigator Award ( awarded by the Energy Technology Division of The Electrochemical Society ) ; 2017 UConn Chemical Engineering Faculty of the Year Award , 2019 USC Chemical Engineering Publication Award ; and 2015–2016 Fulbright Scholar Fellowship .

Available to watch now, The Electrochemical Society, in partnership with Admiral Instruments and Scribner, explore the challenges for the development and deployment of AEM fuel cells
Want to learn more on this subject? Watch now
In recent years, advances in alkaline exchange membrane fuel cells (AEMFCs) with anion exchange membrane (AEM) solid polymer electrolytes have gained traction due to their distinct, and potentially game-changing, advantages over proton exchange membrane fuel cells. There has been growing excitement in the past 2–3 years, especially as AEMFCs have reached a stage in their development where state-of-the-art cells are reaching comparable power densities to proton exchange membrane fuel cells (PEMFCs) and are able to operate stably for more than 1000 hours.
However, AEMFCs still need to address at least three critical issues if they are to be deployed in the field:
Water management in AEMFCs is more complex than PEMFCs and there is a tendency for significant water accumulation and flooding at the anode – sacrificing both performance and longevity.
There is a need to reduce costs significantly below the PEMFCs and doing this will require completely PGM-free catalysts.
Management of CO 2 and mitigation of CO 2 -related performance losses.
This presentation will begin with an introduction to how AEMFCs operate, their similarities and differences to PEMFCs. Then, state-of-the-art performance and durability will be shown along with an explanation for how these two were systematically improved over the past few years due to advances in materials as well as innovations in electrode design and reactor engineering. Next, the three issues above – water management, PGM-free catalysts and CO 2 management – will be discussed, with a focus on the fundamental thermodynamic, kinetic and transport barriers that remain. Finally, an outlook on the future of the technology and important areas for research will be
discussed.
Want to learn more on this subject? Watch now
William (Bill) Mustain is a Professor in the Department of Chemical Engineering at the University of South Carolina (USC). In 2017, he moved to USC from the Department of Chemical and Biomolecular Engineering at the University of Connecticut (UConn) where he was an Associate Professor and the United Technologies Corporation Professor of Engineering Innovation. He joined UConn as an Assistant Professor in 2008 and was tenured and promoted to Associate Professor in 2013. Professor Mustain has worked in several areas related to electrochemical energy generation and storage including: high-capacity materials for lithium-ion batteries, catalysts and supports for proton exchange membrane and anion exchange membrane fuel cells and electrolyzers, electrochemical synthesis of fuels, electrochemical control of biological systems, the purposeful use of carbonates in low-temperature electrochemical systems, and the electrochemical capture and utilization of CO 2 . He has been the PI or co-PI on approximately $10m of externally funded research projects. He has published more than 100 peer-reviewed articles and three book chapters to date and has more than 100 invited and conference talks. He has been the recipient of several awards including the 2009 Illinois Institute of Technology Young Alumnus Award; 2013 US Department of Energy Early Career Award; 2014 Connecticut Quality Improvement Platinum Award; 2014 Supramaniam Srinivasan Young Investigator Award (awarded by the Energy Technology Division of The Electrochemical Society); 2017 UConn Chemical Engineering Faculty of the Year Award, 2019 USC Chemical Engineering Publication Award; and 2015–2016 Fulbright Scholar Fellowship.


physicsworld--2020-09-11--Advanced radiotherapy – at a fraction of the cost - Physics World

EmpowerRT , a social enterprise company spun out from the University of North Carolina ( UNC ) , has an impressive goal : to help resource-limited cancer clinics in developing countries improve radiotherapy , at just 5–10 % of the cost of purchasing modern technology .
Currently , there is a huge disparity in cancer care across the world .
About 70 % of deaths from cancer occur in low- and middle-income countries ( LMICs ) and , according to the World Health Organization , it is these LMICs that will face the highest increase in cancer death rates in @ @ @ @ @ @ @ for this disparity is that many cancer clinics in LMICs still rely on older generation radiotherapy equipment , with no funds available to update to modern digital-based systems and the associated infrastructure .
And while advances in radiation therapy technologies , such as the introduction of intensity-modulated radiotherapy ( IMRT , which has been standard-of-care for years in developed nations ) , can improve tumour targeting and clinical outcomes , such systems are simply too expensive for many cancer clinics in LMICs .
“ This is the really sad truth , ” says @ @ @ @ @ @ @ Chang .
“ Many patients in developing countries die and suffer , not because the world doesn ’ t know how to treat their cancers , but because they have no access to the treatments .
Our mission is to help people in low-resource countries to improve the quality of radiotherapy using existing resources , without spending millions of dollars that they don ’ t have.
” EmpowerRT is tackling this problem by offering a technology that enables any radiation delivery system to provide IMRT , using a low-cost compensator placed in front @ @ @ @ @ @ @ comprises a styrofoam mould filled with tungsten granules .
It can be fabricated using a milling machine , assembled on site and , after treatment , the tungsten can be recycled to treat other patients .
“ The core belief of EmpowerRT is that we can advance cancer care by doing more with less , doing more with what is already available , and doing it simply ” , says Sha .
Similar to modern radiotherapy systems , the IMRT compensator shape is individually designed to attenuate the radiation beam to maximize dose @ @ @ @ @ @ @ to nearby healthy tissue .
“ Using this approach , we can make existing radiation therapy machines in LMICs deliver a more advanced treatment .
That ’ s the beauty of it , ” says Sha .
She explains that the recyclable compensator IMRT solution was developed at UNC before multileaf collimator ( MLC ) -based machines were widely available , and was used in treatments for 14 years and 1400 patients before UNC terminated its use after migrating to digital-based radiotherapy .
“ We developed the recyclable compensator IMRT technology at a @ @ @ @ @ @ @ operating environment that ’ s still used in many low-resource settings .
So we know this technology is feasible in that environment , ” says Sha .
“ We want to give our proven technology a second life that can benefit more cancer patients.
” In addition to the recyclable compensator IMRT technology , EmpowerRT also offers treatment planning software and e-chart , a digital patient chart software designed for manually operated clinics .
“ Our goal is to bring the many benefits of a record and verify system to low-resourced clinics in @ @ @ @ @ @ @ We are also bringing in grid therapy , a novel therapy that benefits large and late-stage tumours , which are more prevalent in developing countries.
” The company also provides extensive training and support , to help sites introduce IMRT – everything from quality assurance and patient selection to setup – in order to establish an effective and safe treatment programme .
EmpowerRT has now installed this technology at its first site – the Cancer Diseases Hospital in Zambia .
The country ’ s sole cancer hospital , it has three basic radiotherapy @ @ @ @ @ @ @ able to deliver IMRT .
The EmpowerRT team offered remote training on the treatment planning software and also travelled to Zambia three times for extended onsite training and dry runs .
Sha notes that the training focused on knowledge transfer : “ we train the trainer , and then watch the trainer train others , ” she explains .
“ The training was excellent and the time spent was more than expected , with various hands-on and ‘ real patient ’ practice cases , ” says Mulape Kanduza , chief medical physicist at @ @ @ @ @ @ @ first impression was ‘ why is this renowned professor from UNC interested in working with our department ?
’ .
Effort was put both by the trainees and trainers and I believe the output is evident.
” Challenges such as machines breaking down and long delays in performing repairs , which are not uncommon in a LMIC environment , exacerbated by COVID-19-related travel restrictions , mean that the Cancer Diseases Hospital has not been able to complete an IMRT patient treatment yet .
“ But we have overcome many unexpected challenges , and @ @ @ @ @ @ @ and radiation therapy technologists all learned a great deal , ” says Sha .
“ They are confident that they can do this new procedure independently , with us remotely doing the review and monitoring .
That ’ s the success.
” “ The future is very positive in that we have created a lasting relation to draw from , ” Kanduza tells Physics World .
“ The positive outcome [ will be ] seeing an IMRT patient treatment being executed and knowing that the outcomes will be much better than treating with @ @ @ @ @ @ @ assurance in the workflow , using the Excel-based e-chart to review treatment records , has allowed us to think differently and to acknowledge change , ” Kanduza adds .
“ One measurable outcome is that EmpowerRT ’ s e-chart system can work in a low-income setting such as ours.
” Looking ahead , EmpowerRT is now in talks with cancer clinics in Nigeria and Indonesia .
The company is also partnering with organizations such as Clinton Health Access Initiative , which has worked for decades to reduce the burden of disease in LMICs @ @ @ @ @ @ @ focuses on global radiotherapy training .
“ We are also writing an NIH small business proposal targeted to feasible and effective cancer solutions in LMICs , ” says Sha .
“ The next step is not only looking for where we can help , but how as a social enterprise company we can continue to grow , to partner with more like-minded global cancer care organizations and make a difference together .
”

EmpowerRT’s founder and president Sha Chang trains staff at the Cancer Diseases Hospital in Zambia to use EmpowerRT’s software. (Courtesy: Cathy Mwaba, Zambia Cancer Diseases Hospital)
EmpowerRT, a social enterprise company spun out from the University of North Carolina (UNC), has an impressive goal: to help resource-limited cancer clinics in developing countries improve radiotherapy, at just 5–10% of the cost of purchasing modern technology.
Currently, there is a huge disparity in cancer care across the world. About 70% of deaths from cancer occur in low- and middle-income countries (LMICs) and, according to the World Health Organization, it is these LMICs that will face the highest increase in cancer death rates in decades to come.
One underlying reason for this disparity is that many cancer clinics in LMICs still rely on older generation radiotherapy equipment, with no funds available to update to modern digital-based systems and the associated infrastructure. And while advances in radiation therapy technologies, such as the introduction of intensity-modulated radiotherapy (IMRT, which has been standard-of-care for years in developed nations), can improve tumour targeting and clinical outcomes, such systems are simply too expensive for many cancer clinics in LMICs.
“This is the really sad truth,” says EmpowerRT’s founder and president Sha Chang. “Many patients in developing countries die and suffer, not because the world doesn’t know how to treat their cancers, but because they have no access to the treatments. Our mission is to help people in low-resource countries to improve the quality of radiotherapy using existing resources, without spending millions of dollars that they don’t have.”
EmpowerRT is tackling this problem by offering a technology that enables any radiation delivery system to provide IMRT, using a low-cost compensator placed in front of the treatment beam. The compensator comprises a styrofoam mould filled with tungsten granules. It can be fabricated using a milling machine, assembled on site and, after treatment, the tungsten can be recycled to treat other patients. “The core belief of EmpowerRT is that we can advance cancer care by doing more with less, doing more with what is already available, and doing it simply”, says Sha.
The Styrofoam compensator mould (left) filled with recyclable tungsten granules (right). (Courtesy: Cathy Mwaba, Zambia Cancer Diseases Hospital)
Similar to modern radiotherapy systems, the IMRT compensator shape is individually designed to attenuate the radiation beam to maximize dose to the tumour target while minimizing dose to nearby healthy tissue. “Using this approach, we can make existing radiation therapy machines in LMICs deliver a more advanced treatment. That’s the beauty of it,” says Sha. She explains that the recyclable compensator IMRT solution was developed at UNC before multileaf collimator (MLC)-based machines were widely available, and was used in treatments for 14 years and 1400 patients before UNC terminated its use after migrating to digital-based radiotherapy.
“We developed the recyclable compensator IMRT technology at a time when we were in a manual operating environment that’s still used in many low-resource settings. So we know this technology is feasible in that environment,” says Sha. “We want to give our proven technology a second life that can benefit more cancer patients.”
In addition to the recyclable compensator IMRT technology, EmpowerRT also offers treatment planning software and e-chart, a digital patient chart software designed for manually operated clinics. “Our goal is to bring the many benefits of a record and verify system to low-resourced clinics in LMICs,” says Sha. “We are also bringing in grid therapy, a novel therapy that benefits large and late-stage tumours, which are more prevalent in developing countries.”
The company also provides extensive training and support, to help sites introduce IMRT – everything from quality assurance and patient selection to setup – in order to establish an effective and safe treatment programme.
Inaugural installation
EmpowerRT has now installed this technology at its first site – the Cancer Diseases Hospital in Zambia. The country’s sole cancer hospital, it has three basic radiotherapy machines, none of which were previously able to deliver IMRT.
The EmpowerRT team offered remote training on the treatment planning software and also travelled to Zambia three times for extended onsite training and dry runs. Sha notes that the training focused on knowledge transfer: “we train the trainer, and then watch the trainer train others,” she explains.
Radiotherapy training at the Cancer Diseases Hospital in Zambia. (Courtesy: Cathy Mwaba, Zambia Cancer Diseases Hospital)
“The training was excellent and the time spent was more than expected, with various hands-on and ‘real patient’ practice cases,” says Mulape Kanduza, chief medical physicist at the Cancer Diseases Hospital. “My first impression was ‘why is this renowned professor from UNC interested in working with our department?’. Effort was put both by the trainees and trainers and I believe the output is evident.”
Challenges such as machines breaking down and long delays in performing repairs, which are not uncommon in a LMIC environment, exacerbated by COVID-19-related travel restrictions, mean that the Cancer Diseases Hospital has not been able to complete an IMRT patient treatment yet. “But we have overcome many unexpected challenges, and the Zambia team of doctors, physicists and radiation therapy technologists all learned a great deal,” says Sha. “They are confident that they can do this new procedure independently, with us remotely doing the review and monitoring. That’s the success.”
“The future is very positive in that we have created a lasting relation to draw from,” Kanduza tells Physics World. “The positive outcome [will be] seeing an IMRT patient treatment being executed and knowing that the outcomes will be much better than treating with other conventional techniques.”
“Improved quality assurance in the workflow, using the Excel-based e-chart to review treatment records, has allowed us to think differently and to acknowledge change,” Kanduza adds. “One measurable outcome is that EmpowerRT’s e-chart system can work in a low-income setting such as ours.”
Looking ahead, EmpowerRT is now in talks with cancer clinics in Nigeria and Indonesia. The company is also partnering with organizations such as Clinton Health Access Initiative, which has worked for decades to reduce the burden of disease in LMICs, and Rayos Contra Cancer, which focuses on global radiotherapy training.
“We are also writing an NIH small business proposal targeted to feasible and effective cancer solutions in LMICs,” says Sha. “The next step is not only looking for where we can help, but how as a social enterprise company we can continue to grow, to partner with more like-minded global cancer care organizations and make a difference together.”


physicsworld--2020-09-11--A new approach to Hall measurement - Physics World

This video highlights the MeasureReady M91 FastHall , a revolutionary , all‑in-one Hall analysis instrument that delivers significantly higher levels @ @ @ @ @ convenience to researchers involved in the study of electronic materials .
The M91 FastHall measurement @ @ @ @ @ necessary HMS functions into a single instrument , automating and optimizing the measurement process , @ @ @ @ @ parameters .
With Lake Shore ’ s patented new FastHall measurement technique , the M91 @ @ @ @ @ Hall effect is measured by eliminating the need to switch the polarity of the applied @ @ @ @ @ .
This breakthrough results in faster and more accurate measurements , especially when using high @ @ @ @ @ measuring very low mobility materials .

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


physicsworld--2020-09-11--The best way to slice a watermelon, how to float yourself with balloons, shining light on whisky - P

The best way to slice a watermelon, how to float yourself with balloons, shining light on whisky - Physics World

What is the fairest way to slice up a watermelon ?
A juicy question that you might never have considered unless you are suddenly given the task at a children ’ s birthday party .
Well , physicists in Belgium , France and Italy have now tackled the problem using geometry and calculus .
After cutting the whole watermelon in half along its length and then in the middle to yield four equal quarters , the researchers discovered that this “ half rule ” fell away when then trying to slice the watermelon up into equal thin portions .
Instead @ @ @ @ @ @ @ .
So for a spheroid watermelon of length 10 cm , for two slices , the first slice should be made at 3.5 cm along the length but for three slices , the first slice should be 2.1 cm and the second 4.2 cm .
After doing the calculations , the researchers tested them on a 4 kg watermelon and used Archimedes principle to confirm the slice volumes were equal .
Eureka !
A week or so ago the illusionist David Blaine floated over the Arizona desert while hanging on to a bunch @ @ @ @ @ @ @ want to do this – and I am not recommending it – how many balloons would you need ?
The physicist Rhett Allain has done all the heavy lifting and provides the answer in “ Let ’ s calculate how many balloons David Blaine needed to float ” .
Counterfeit drinks cost the UK economy more than £200 million in lost revenue each year and this is a real concern in Scotland , where whisky production is a multi-billion pound industry .
Indeed , rare bottles of whisky can fetch as much as @ @ @ @ @ @ @ on knowing what is in their bottles – but do not necessarily want to open them to find out .
Now , researchers at Scotland ’ s University of St Andrews have developed a new laser-based spectroscopy technique that produces a chemical fingerprint of a whisky , without having to open the bottle .
Previous attempts at doing this had not been successful because of the strong signal generated by the laser striking the glass .
The team get around this by using a ring-shaped laser beam that is tightly focussed on a @ @ @ @ @ @ @ only gathering the spectroscopic signal from this focal point , they avoided the signal from the glass .
You can read more in a paper published in Analytical Methods .

A cut above: how to share a watermelon. (Courtesy: Timoteo Carletti)
What is the fairest way to slice up a watermelon? A juicy question that you might never have considered unless you are suddenly given the task at a children’s birthday party. Well, physicists in Belgium, France and Italy have now tackled the problem using geometry and calculus. After cutting the whole watermelon in half along its length and then in the middle to yield four equal quarters, the researchers discovered that this “half rule” fell away when then trying to slice the watermelon up into equal thin portions. Instead they found a ”2/3 rule”. So for a spheroid watermelon of length 10 cm, for two slices, the first slice should be made at 3.5 cm along the length but for three slices, the first slice should be 2.1 cm and the second 4.2 cm. After doing the calculations, the researchers tested them on a 4 kg watermelon and used Archimedes principle to confirm the slice volumes were equal. Eureka!
A week or so ago the illusionist David Blaine floated over the Arizona desert while hanging on to a bunch of helium balloons. Now if you want to do this – and I am not recommending it – how many balloons would you need? The physicist Rhett Allain has done all the heavy lifting and provides the answer in “Let’s calculate how many balloons David Blaine needed to float”.
Counterfeit drinks cost the UK economy more than £200 million in lost revenue each year and this is a real concern in Scotland, where whisky production is a multi-billion pound industry. Indeed, rare bottles of whisky can fetch as much as £1 million, so collectors are keen on knowing what is in their bottles – but do not necessarily want to open them to find out.
Now, researchers at Scotland’s University of St Andrews have developed a new laser-based spectroscopy technique that produces a chemical fingerprint of a whisky, without having to open the bottle. Previous attempts at doing this had not been successful because of the strong signal generated by the laser striking the glass. The team get around this by using a ring-shaped laser beam that is tightly focussed on a small region in the liquid. By only gathering the spectroscopic signal from this focal point, they avoided the signal from the glass. You can read more in a paper published in Analytical Methods.


physicsworld--2020-09-14--Spin valve uses coupled quantum dots and tiny magnetic fields - Physics World

Researchers in Switzerland and Italy have developed a method for generating currents of electrons with a known quantum spin without the need for large external magnetic fields .
This could enable the development of devices that are compatible with superconducting electronic elements , paving the way for the next generation of highly efficient electronics .
Following the discovery of giant magnetoresistance as well as the observation of spin injection and detection in metals in the late 1980s , a field of research known as “ spintronics ” emerged dedicated to creating practical devices that exploit electron spin .
Semiconductor-based spintronics @ @ @ @ @ @ @ semiconductors can be integrated within modern-day electronics , thus improving the efficiency and storage capacity of devices .
But in order to make useful spintronics devices , researchers need to be able to control and detect the spin state of electrons with a high level of accuracy .
One method for controlling the electron spin current is a device known as the “ spin valve ” , which usually consists of a non-magnetic material sandwiched between ferromagnetic materials .
This material configuration allows electrons with one spin to propagate through the device , @ @ @ @ @ @ @ scattered away .
This occurs because spin propagation depends on the alignment of the magnetic moments in the ferromagnet .
Thus , a “ spin polarized current ” is produced .
This is a flow of electrons that , in theory , all are in a set spin state ( all spin-up or all spin-down ) .
However , these types of spin valve are either not very efficient or require very large polarizing magnetic fields both imposing severe limitations on experiments — for example , experiments involving material systems that are sensitive @ @ @ @ @ @ @ and achieve a highly spin-polarized current , researchers are looking for alternative methods to create spin valves using semiconductor materials .
Now , physicists at the University of Basel along with collaborators at the National Enterprise for nanoScience and nanoTechnology have created a device that can control electron spin currents without the need for large external magnetic fields and with a high efficiency .
In a recent paper published in Communications Physics , they describe how a pair of coupled quantum dots formed in an indium arsenide ( InAs ) nanowire with nearby @ @ @ @ @ @ @ spin valve with an electrically tuneable spin polarization of up to ±80 % .
The team created the quantum dots by electrically defining two areas where electrons in the nanowire are confined in all three spatial directions .
They then employed ferromagnetic side gates to generate small local magnetic fields across each dot .
This gate-based configuration means that only very small magnetic field of up to 40 mT are needed to obtain a very high efficiency .
The device operates by generating a spin-polarized tunnel current using the first dot , which @ @ @ @ @ @ @ .
By magnetizing the ferromagnetic split gates in parallel or anti-parallel , the researchers can decide whether electrons of a certain spin can pass through each part of the device .
The probability that an electron with that spin tunnels through both dots can be controlled using the ferromagnetic side gates , allowing a spin-polarized current to flow when they are aligned but no current at all if they are anti-parallel .
The researchers were able to “ tune ” the device by experimenting with different applied fields and gate voltages .
They @ @ @ @ @ @ @ polarization efficiency with the potential to reach the theoretical limit of 100 % .
This type of spin valve could be very useful in applications for which magnetic fields can have a drastic impact on the material characteristics – such as suppressing superconductivity or altering electronic band structures .
The manipulation of electron spin with such small magnetic fields may allow researchers to develop new quantum technologies that utilize spin-based quantum phenomena such as entanglement and the confirmation of Majorana fermions in topological superconductors along with facilitating the investigation into new unexplored physics @

Spin device: in this diagram of the spin valve the nanowire runs between a source and drain (both shown in gold) and the locations of the two quantum dots on the nanowire are denoted by the dashed ellipses. The brown bars are nanomagnets and the white arrows show their magnetizations. In this example, spin-up electrons can travel across the nanowire whilst spin-down electrons cannot. (Courtesy: University of Basel Department of Physics)
Researchers in Switzerland and Italy have developed a method for generating currents of electrons with a known quantum spin without the need for large external magnetic fields. This could enable the development of devices that are compatible with superconducting electronic elements, paving the way for the next generation of highly efficient electronics.
Following the discovery of giant magnetoresistance as well as the observation of spin injection and detection in metals in the late 1980s, a field of research known as “spintronics” emerged dedicated to creating practical devices that exploit electron spin. Semiconductor-based spintronics systems have garnered particular research interest because semiconductors can be integrated within modern-day electronics, thus improving the efficiency and storage capacity of devices. But in order to make useful spintronics devices, researchers need to be able to control and detect the spin state of electrons with a high level of accuracy.
Controlling electron spin
One method for controlling the electron spin current is a device known as the “spin valve”, which usually consists of a non-magnetic material sandwiched between ferromagnetic materials. This material configuration allows electrons with one spin to propagate through the device, while the opposite spin is reflected or scattered away. This occurs because spin propagation depends on the alignment of the magnetic moments in the ferromagnet. Thus, a “spin polarized current” is produced. This is a flow of electrons that, in theory, all are in a set spin state (all spin-up or all spin-down).
Spin-valve trio: Andreas Baumgartner (left), Arunav Bordoloi (centre) and Christian Schonenberger. (Courtesy: University of Basel Department of Physics)
However, these types of spin valve are either not very efficient or require very large polarizing magnetic fields both imposing severe limitations on experiments — for example, experiments involving material systems that are sensitive to magnetic fields. To overcome this and achieve a highly spin-polarized current, researchers are looking for alternative methods to create spin valves using semiconductor materials.
Tiny magnetic fields
Now, physicists at the University of Basel along with collaborators at the National Enterprise for nanoScience and nanoTechnology have created a device that can control electron spin currents without the need for large external magnetic fields and with a high efficiency. In a recent paper published in Communications Physics, they describe how a pair of coupled quantum dots formed in an indium arsenide (InAs) nanowire with nearby individual nanomagnets can be used as a spin valve with an electrically tuneable spin polarization of up to ±80%.
The team created the quantum dots by electrically defining two areas where electrons in the nanowire are confined in all three spatial directions. They then employed ferromagnetic side gates to generate small local magnetic fields across each dot. This gate-based configuration means that only very small magnetic field of up to 40 mT are needed to obtain a very high efficiency.
The device operates by generating a spin-polarized tunnel current using the first dot, which is then detected by the second dot. By magnetizing the ferromagnetic split gates in parallel or anti-parallel, the researchers can decide whether electrons of a certain spin can pass through each part of the device. The probability that an electron with that spin tunnels through both dots can be controlled using the ferromagnetic side gates, allowing a spin-polarized current to flow when they are aligned but no current at all if they are anti-parallel. The researchers were able to “tune” the device by experimenting with different applied fields and gate voltages. They were able to achieve a high spin polarization efficiency with the potential to reach the theoretical limit of 100%.
New quantum technologies
This type of spin valve could be very useful in applications for which magnetic fields can have a drastic impact on the material characteristics – such as suppressing superconductivity or altering electronic band structures. The manipulation of electron spin with such small magnetic fields may allow researchers to develop new quantum technologies that utilize spin-based quantum phenomena such as entanglement and the confirmation of Majorana fermions in topological superconductors along with facilitating the investigation into new unexplored physics.