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Hier — 3 avril 2020Physics World

Backpack computers for small animals, decade of LHC physics in numbers, post manuscript submission press conference - Physics World

Looking out my window at the garden during this lock down, I am a bit envious of the birds that are free to come and go as they please. But what if I wanted to know what that fat wood pigeon gets up to when it is not feasting on my newly seeded lawn.

Simon Ripperger and colleagues at the Ohio State University have created a tiny wireless backpack computer  that can be used to track animals in the wild (see figure). The device was created to study the social habits of the vampire bat, but I’m guessing it would also work on a pigeon.

Has it really been ten years since the Large Hadron Collider (LHC) at CERN started taking data? To celebrate a decade of achievement, Sarah Charley has charted progress at CERN in numbers.

Did you know that since 2010, exactly 2947 summer students have worked at CERN? They probably played a role in drinking the 10 million cups of coffee served at CERN restaurants in the past decade and hopefully had a hand in producing 2725 scientific papers.

Collisions at the LHC produced about 8 million Higgs particles, at least according to the Standard Model, and physicists had to sift through 278 petabytes of data to find a few Higgs to study.

Another figure that Charley came up with is the total mass of all the protons that have whizzed around the LHC since 2010. Any guesses?

You can find the answer in “10 years of LHC physics, in numbers” which appears in Symmetry.

Post Manuscript Submission Press Conference. Looking to use this momentum and take it into future papers.. pic.twitter.com/nOVRH5xMLN

— Ciaran Fairman, PhD (@CiaranFairman) April 2, 2020

A few weeks ago, I shared a video by the Irish medical researcher Ciaran Fairman that imagined a post-game analysis of a talk at a scientific conference. Now, Fairman is back in the above video with a similar take on the submission of a scientific paper for peer review. I like his comments on a certain referee – “you’re going to have to reference their work, there’s really no point in arguing with them”.

The post Backpack computers for small animals, decade of LHC physics in numbers, post manuscript submission press conference appeared first on Physics World.

Online Demo: 10 years of PeakForce Tapping – Imaging in Liquid - Physics World

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Click here to register

Wed, Apr 8, 2020 2:00 PM – 3:00 PM BST

Join this online demonstration to learn about the theoretical and practical PeakForce technology for Imaging in Liquid This webinar will introduce PeakForce Tapping technology with Scan Asyst mode for liquid measurement. A short introduction will describe the PeakForce principle and what probes can be used. Live measurement samples will be studied and relevant parameters will be explained.

Who should attend:

-Everyone who has interest in AFM

-PeakForce Tapping users who want to extend their knowledge

Presenter:


Dr. Samuel Lesko
Senior Application Development Manager


Dr. Udo Volz
Application Scientist

The post Online Demo: 10 years of PeakForce Tapping – Imaging in Liquid appeared first on Physics World.

Quantum computing meets particle physics for LHC data analysis - Physics World

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An international collaboration is exploring how quantum computing could be used to analyse the vast amount of data produced by experiments on the Large Hadron Collider (LHC) at CERN. The researchers have shown that a “quantum support vector machine” can help physicists make sense out of the huge amounts of information generated at CERN.

Experiments on the LHC can produce a staggering one petabyte per second of data from about one billion particle collisions per second. Many of these data must be discarded because the experiments are only able to focus on a subset of collision events. Nevertheless, CERN’s data analysis now relies on close to one million CPU cores working in 170 computer centres around the globe.

The LHC is currently undergoing an upgrade that will boost the collision rate. The computing power necessary to process and analyze the additional data is expected to increase by a factor of 50-100 by 2027. While improvements in current technologies will address a small part of this gap, researchers at CERN will have to find new and smarter ways to address the computing challenge – which is where quantum computing comes in.

Quantum collaboration

In 2001 the lab set up a public-private partnership called CERN openlab to accelerate the development of new computing technologies needed by CERN’s research community. One of the several leading technology companies involved in this collaboration is IBM, which is also a major player in the field of quantum computing research and development.

Quantum computers could, in principle, solve certain problems in much shorter times than conventional computers. While significant technological challenges must be overcome to create practical quantum computers, IBM and a handful of other companies have build commercial quantum computers that can already do calculations.

Federico Carminati, a computer physicist at CERN and CERN openlab’s chief innovation officer, explains the lab’s interest in a quantum solution: “We are looking into quantum computing, as it might provide a possible solution to our computing power problem”. He told Physics World that CERN openlab is not looking to try to implement a powerful quantum computer tomorrow, but rather to play “the medium-long game” to see what is possible. “We can try to simulate nuclear physics, the scattering of the nuclei, maybe even simulate quarks and the fundamental interactions,” he explains.

CERN openlab and IBM started working together on quantum computing in 2018. Now, physicists at the University of Wisconsin led by Sau Lan Wu, CERN, IBM Research in Zurich, and Fermilab near Chicago are looking at how quantum machine learning could be used to identify Higgs boson events in LHC collision data.

Promising results

Using IBM’s quantum computer and quantum computer simulators, the team set out to apply the quantum support vector machine method to this task. This is a quantum version of a supervised machine learning system that is used to classify data.

“We analysed simulated data of Higgs experiments with the aim of identifying the most suited quantum machine learning algorithm for the selection of events of interest, which can be further analysed using conventional, classical, algorithms,” explains Panagiotis Barkoutsos of IBM Research.

The preliminary results of the experiment were very promising. Five quantum bits (qubits) on an IBM quantum computer and quantum simulators were applied to the data.. “With our quantum support vector machine, we analyzed a small training sample with over 40 features and five training variables. The results come very close to – and sometimes even better than – the ones obtained using the best known equivalent classical classifiers and were obtained efficiently and in short time,” says Barkoutsos.

Seeking out new physics

Discovering the Higgs boson in the LHC data is often compared to “finding a needle in a haystack”, given its very weak signal. Indeed, most of the vast amount of computing time used by LHC physicists so far went to the Higgs boson analysis.

An important goal of the LHC is to test the Standard Model of particle physics to the breaking point in a search for new physics – and quantum computing could play an important role. “This is exactly something we are aiming for, the very fine analysis of complex data that would produce anomalies, helping us to improve the Standard Model or to go beyond it,” concludes Carminati.

The team has not yet published its results, but a manuscript is being finalized. Work is also underway using a greater number of qubits, more training variables and larger sample sizes.

The post Quantum computing meets particle physics for LHC data analysis appeared first on Physics World.

Chemical characterization of heterogenous polymeric materials on the nanoscale using photothermal AFM-IR - Physics World

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Click here to register

Wed, Apr 8, 2020 9:00 AM – 10:00 AM BST

Join this webinar to learn how Photothermal AFM-IR can provide new insights into your polymer research This webinar will cover numerous applications in the field of polymer characterization both in academia and industry. In order to illustrate the broad applicability, we will discuss selected examples in detail, ranging from phase separation in polymer blends/block copolymers, reverse engineering in multilayer films, fibers and thin film characterization. Photothermal AFM-IR can provide nanoscale chemical information with highly resolved IR spectra, that directly correlate to FT-IR transmission spectroscopy.

Presenter:


Dr. Miriam Unger
NanoIR Application Scientist


Dr. Hartmut Stadler
Application Scientis

The post Chemical characterization of heterogenous polymeric materials on the nanoscale using photothermal AFM-IR appeared first on Physics World.

Nanoindentation of Metallic Samples - Physics World

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Click here to register

Tue, Apr 7, 2020 2:00 PM – 3:00 PM BST

Nanoindentation of metallic samples is closely related to hardness testing methods such as Vickers. The Vickers hardness test requires an imaging method to determine the size of the indentation cup. This implies that the Vickers hardness test is limited to larger indentation cups. Nanoindenation not only eliminates this shortfall by determining the size of the indentation cup from measurements of load and displacement, it also is much easier to automate the nanoindentation testing and the analysis of mechanical data.

This session contains an introduction into hardness testing, the indentation analysis following Oliver&Pharr (1992) and demonstrates the benefits of hardness testing at nanoscale for metallic samples.

Presenter:


Dr. Ude Dirk Hangen
Nanomechanical Application Manager


Dr. Rhys Jones.
Nanoindentation Product Sales Specialist

The post Nanoindentation of Metallic Samples appeared first on Physics World.

À partir d’avant-hierPhysics World

Remembering Philip Anderson, meeting an extragalactic astronomer who advises the government - Physics World

In this episode of the Physics World Weekly podcast we look back on the life of the prodigious condensed-matter physicist Philip Anderson, who died age 96 on 29 March.

We also have an exclusive interview with Professor of Extragalactic Astronomy at the University of Bath, Carole Mundell, who talks about her research on gamma-ray bursts. Mundell is also Chief Scientific Advisor to the UK’s Foreign and Commonwealth Office and explains how she translates science into scientific advice on issues of national importance.

We round off the programme by laughing along with a few physicists who have admitted to doing some pretty stupid things.

The post Remembering Philip Anderson, meeting an extragalactic astronomer who advises the government appeared first on Physics World.

Critical research hit as COVID-19 forces physics labs to close - Physics World

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The physical sciences have not evaded the disturbance of daily life as a result of COVID-19 – the disease caused by the SARS-CoV-2 virus that is sweeping the globe. Government laboratories have either shut down or required employees to work from home while closing to visitors. The schedules of forthcoming space missions have been put at risk. Administrators of major telescopes have restricted or postponed critical observations. And individual postgraduates and junior scientists have seen their career paths put on hold as universities shut their doors.

In the US, national laboratories overseen by the Department of Energy (DOE) have suffered significant disruption. That occurred initially as a result of geography, with the virus having made its first deadly impact in the state of Washington. Most staff at the DOE’s Pacific Northwest National Laboratory in Richland, for example, have been working at home since early March. California’s Bay Area also emerged as an early hotspot.

A directive from California Governor Gavin Newsome that prohibited inessential travel and meetings led the SLAC, Berkeley, Lawrence Livermore National Laboratories, and the local branch of Sandia National Laboratory effectively to shut down, with most of their employees now working remotely at home too. There are exceptions, however. The Berkeley Lab is currently in a “safe and stable standby” status, with only critical work occurring on-site and most staff working remotely. This week, the lab’s Advanced Light Source began operating a limited number of beamlines for three days a week for users that are developing therapeutics to help combat the SARS-CoV-2 virus.

Other DOE labs have either restricted visitors, operated largely off-site or closed down as the virus created fresh hotspots. New York and New Jersey soon followed Washington state in exposure. The Princeton Plasma Physics Laboratory shut down on 13 March,  requiring all its employees to work at home. A week later, Brookhaven National Laboratory responded to New York Governor Andrew Cuomo’s order that employees in “non-essential” jobs should stay at home. A subsequent order by Illinois Governor J B Pritzker also forced the Argonne and Fermilab facilities to restrict their operations. Meanwhile, the Oak Ridge National Laboratory in Tennessee and the Idaho National Laboratory have closed to visitors, researchers and the general public alike.

‘Heroes’ work’

NASA has been similarly affected, with greater impact on specific missions. On 19 March NASA administrator Jim Bridenstine announced plans to put all the agency’s centres under “stage 3 status”, which requires all but “mission essential” staff to work remotely. “We are going to take care of our people,” Bridenstine said. “That’s our first priority.”

An immediate result of NASA’s announcement was the temporary closures of the Michoud Assembly Facility in New Orleans and the nearby Stennis Space Center in Mississippi when the number of COVID-19 cases rose in the area. A result of the closures, Bridenstine noted, would be “temporarily suspension of production of the Space Launch System and Orion Hardware” – key components of the agency’s plan to land astronauts on the Moon in 2024. Analysts had already questioned the viability of that schedule under normal conditions, but it now seems even more doubtful.

A more immediate mission – Mars 2020 – remains on schedule. The $2.5bn project, which includes the newly named Perseverance rover, has a 20-day launch window that starts on 17 July. Failure to meet that window would delay the flight by two years. The mission has “the very highest priority”, Lori Glazer, head of NASA’s planetary science division, told a virtual meeting. “We’re going to ensure that we meet that launch window in July.” The project’s engineers are doing “heroes’ work” in maintaining that schedule, said NASA’s science head Thomas Zurbuchen.

The schedule of another prestige project, the James Webb Space Telescope (JWST), is less certain. California’s state-wide lockdown has applied to Northrop Grumman Aerospace Systems in Redondo Beach, which had been carrying out shaking tests on the $8.8bn observatory. A successor of the Hubble Space Telescope, JWST has already suffered numerous delays and is unlikely to meet its current launch date of March 2021.

Several observatories belonging to the Event Horizon Telescope have also closed down owing to the coronavirus, with the organization having cancelled its observing campaign planned to take place from late March into April. “We will have to wait for March 2021 to try again,” the organization said in a statement. Elsewhere in the world of astronomy, the Atacama Large Millimetre/submillimetre Array in Chile has suspended operations, as has the Association of Universities for Research in Astronomy, which has stopped  observations at several of the telescopes it oversees and halted construction of the Vera C Rubin Observatory in Chile.

Meanwhile, the Laser Interferometer and Gravitational-wave Observatory sites in Hanford, Washington and Livingston, Louisiana, suspended observations on 27 March as did the Virgo detector in Italy. However, operations at the Kamioka Gravitational Wave Detector in northern Japan are still ongoing.

Moving online

The need for social distancing has impacted events organised by scientific societies too. The American Physical Society, which called off its March meeting at short notice, has cancelled its April meeting, but is planning some remote sessions. And the American Astronomical Society has converted its early June meeting to a fully virtual event.

Academic institutions face their own coronavirus issues. Many research universities have moved to virtual operation. Those decisions have put particular pressure on postgraduate students who need to be on-site to perform their research. Some institutions, such as Brown University and the University of Alabama at Birmingham, have frozen hiring. In late March, a group of four organizations representing universities and medical colleges called on Congress to increase spending on research by government agencies.

The $2 trillion rescue package that President Donald Trump signed on 27 March includes some relief. It grants $100m to DOE labs, $75m for National Science Foundation grants, $66m for programmes of the National Institute of Standards and Technology as well as a fund worth $14bn for universities. Observers suggest that those amounts, while welcome, are too small. But the likelihood that Congress will pass another rescue package gives the scientific community some hope of extra support.

European impact

The impact of COVID-19 is, of course, not just impacting US labs. Most labs in Europe have also closed their doors too. The CERN particle-physics lab near Geneva has now reduced all activities on-site to those that are essential for the safety and security of the lab. CERN was moving to the latter parts of a long shutdown in preparation for a major upgrade to the lab’s Large Hadron Collider. Those activities have now been reduced, with officials at CERN working out how the impact will affect the timeline of the upgrade project, which was due to be complete in the mid 2020s. The CERN Council also announced in late March that it has postponed the release of the European strategy update that was due to be released in May.

Yet, a few major projects are still continuing to some degree. Mission controllers at the European Space Agency’s European Space Operations Centre in Darmstadt, Germany, are planning to test instruments on the agency’s Bepicolombo mission to Mercury as it completes a fly-by of Earth on 10 April – albeit with limited personnel. The ITER fusion experiment being built in Cadarache has cancelled all on-site visitors and onsite meetings, but is continuing with “critical responsibilities and functions”. Indeed, the project is still managing to undertake some construction tasks and has taken delivering of magnet components that have arrived from member states. Yet it looks likely that the SARS-CoV-2 virus will put back the start of operations that are currently planned for 2025.

The European Spallation Source, currently under construction in Lund, Sweden, has also put in place measures for staff to work remotely as well as cancelling visits to the site. Yet work is still continuing, with workers having recently installed the water tanks that are used for the proton target. Other neutron and X-ray synchrotrons facilities in Europe have closed such as the Institut Laue–Langevin and the European Synchrotron Radiation Facility, both in Grenoble, France, as well as the ISIS neutron source in Oxfordshire, UK.

Yet some facilities remain open for scientists to carry out research on the SARS-CoV-19 virus. These include the Paul Scherrer Institute in Switzerland, the UK’s Diamond Light Source and the MAX IV synchrotron in Sweden, which are all fast-tracking relevant proposals.

The post Critical research hit as COVID-19 forces physics labs to close appeared first on Physics World.

Titanic stellar explosion scrambles magnetic fields - Physics World

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An unusually energetic gamma-ray burst (GRB) has prompted astrophysicists to rethink the role of magnetic fields in these enormous stellar explosions. Observations made in the burst’s immediate aftermath show that key features of its associated magnetic field mysteriously vanished – a phenomenon that cannot be explained by current theories of how such fields form and evolve.

On 14 January 2019, NASA’s early-warning Swift satellite spotted a flash of gamma rays from an exploding massive star in a galaxy 4.5 billion light years away. Such flashes occur when a star’s iron core collapses into a stellar-mass black hole, producing two relativistic beams of strongly-magnetized particles. These beams generate gamma rays through synchrotron radiation, and as they shoot outwards from the collapsing core, the particles in them collide with circumstellar material shed by the star in the run-up to its explosion. The resulting shock creates an optical afterglow that can linger for months.

As soon as Swift detected the burst, which was designated as GRB 190114C, it automatically alerted a host of telescopes on the ground. Within 32 seconds, the MASTER telescopes in the Canary Islands and South Africa were in position and recording the burst’s afterglow.

This fast response has become standard within GRB astronomy, but the data proved anything but. Based on previous observations, astrophysicists expected the afterglow light to be polarized — perhaps by as much as 30 per cent, although the exact figure depends on the strength and structure of the GRB’s magnetic field. The polarimeters on the MASTER telescopes, however, initially measured a polarization of only 7.7 percent. A minute later, when the Liverpool Telescope in the Canary Islands began taking data on the burst, the polarization had dropped to just two percent, and it remained at this marginal level for the remainder of the observations.

That wasn’t the only odd feature about GRB 190114C. When another facility in the Canary Islands, the MAGIC telescopes, began taking data on the afterglow, it measured incredibly energetic emissions – in the tera-electron-volt (TeV) range – from inverse Compton scattering, which occurs when photons collide with electrons in the circumstellar material. This is the first time such emissions have been detected at such high energies in a GRB.

Shock physics

Image showing two galaxies as bright, pixellated streaks against a black background
Unusual neighbourhood. A Hubble Space Telescope image of the afterglow of GRB 190114C, located in an interacting galaxy 4.5 billion light years away. (Courtesy: NASA/ESA/V Acciari et al./ICRAR).

In a paper published today in The Astrophysical Journal, researchers led by Nuria Jordana of the University of Bath, UK, propose a partial solution to the mystery surrounding GRB 190114C. “We speculate that the low polarization is caused by the catastrophic dissipation of magnetic energy, which destroys the order of the magnetic fields and powers the afterglow,” Jordana tells Physics World.

The picture she and her colleagues paint is one of shockwaves bouncing around the circumstellar material. At some point in the 31 seconds before observations began, the blast wave from the stellar explosion struck this material. Pure kinetic energy allowed the jet and much of the forward shock to pummel through, but part of the wave was reflected, forming a so-called reverse shock.

Since localized disturbances scramble the forward shock’s magnetic field in random orientations, the forward shock is never polarized. The reverse shock, however, should still carry the magnetic field ejected by the newly-formed black hole.

In the case of GRB 190114C, something seems to have caused that magnetic field to catastrophically dissipate and dump its energy into the emission from the afterglow – which would explain the unusually high TeV energies. Jordana and colleagues infer that the weak polarization measured between 52 seconds and 109 seconds after the burst was the remnant of the large-scale magnetic field ejected from the black hole.

Looking for causes

The exact cause of the magnetic field collapse remains uncertain. According to Jordana, although the findings hint at a “universal role” for magnetic fields in GRBs, “the survival of the jet’s magnetic field must depend on additional, as yet unknown, physical factors”. She also points out that the polarization of the early optical afterglow has so far been measured in only a handful of GRBs. A larger sample will, she says, be needed to better understand the mechanisms that drive it.

Andrew Levan, an astrophysicist at Radboud University in the Netherlands who co-authored an earlier paper describing the TeV emission, says that the apparent lack of polarization is “a little surprising”, especially given what he describes as the “very early and sensitive observations” of the GRB’s afterglow. Levan’s group found that GRB 190114C occurred in the central region of a galaxy that is interacting with another galaxy – an unusual location, since GRBs tend to be caused by the destruction of massive stars with low abundances of heavy elements, and these are usually only found in less chemically-evolved galaxies. Levan says it’s “plausible” that GRB 190114C’s environment and unusual characteristics could somehow be linked. However, he adds, “it’s a very difficult problem to explain exactly how the field may have collapsed in this case”.

The post Titanic stellar explosion scrambles magnetic fields appeared first on Physics World.

Spiral patterns in living cells could be used to create biological computers - Physics World

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Ripples that appear on the surfaces of newly fertilized eggs closely resemble those found in other physical systems – according to Nikta Fakhri and colleagues at the Massachusetts Institute of Technology. The team discovered the similarity through statistical analysis of the spiral patterns produced by active proteins in newly fertilized starfish eggs. The researchers say that their discovery could lead to the development of biological computers that use ripples to process information.

When the egg cells of many species are fertilized, complex ripples are often propagate across their surfaces (cell membranes) before cell division begins. These waves are produced by a protein called Rho-GTP. This protein mostly sits inactive in the cell’s cytoplasm, but rapidly springs to action and attaches itself to the cell membrane when a separate hormone indicates cell division should begin. These ripples are known to produce intricate patterns as they propagate, but until now, the physical characteristics of the patterns have remained largely unexplored.

In their study, Fakhri’s team analysed the patterns in detail in fertilized starfish eggs, which are particularly large and easy to observe. To do this, they injected egg cells with a fluorescent marker that attached itself to Rho-GTP. Then they subjected the eggs to the relevant hormone in varying concentrations. In each experiment, they saw that concentrated waves of Rho-GTP oscillated out of moving central points to create spiral patterns. The team describes these centres as “topological defects” – freely-moving points where the molecules in a cell’s membrane do not join up seamlessly.

Universal laws

Fakhri’s group also observed that many spirals move across the membrane at a time. Some of the spirals arise spontaneously in pairs that move in opposite directions, whereas other pairs collide head-on, annihilating each other. After creating animations of the process, the team performed a statistical analysis of the motions of the spirals and topological defects. They discovered that these dynamics can be described by existing mathematical theories describing the dynamics of vortices. This suggested that the system’s behaviour is governed by the same universal laws as a wide variety of other, seemingly unrelated physical systems, albeit on widely differing scales.

The team found that the observed patterns were similar to turbulent vortices in the Earth’s oceans and atmosphere. The patterns also propagated in a way similar to electrical signals in the heart and brain. Perhaps more surprisingly, the velocities of clusters of spiralling waves resembled those found in quantum fluids. With further research, the team hopes that new techniques could emerge for manipulating these dynamics. If achieved, the biological ripples could be made to convey information and perform calculations in ways similar to quantum computers.

“Perhaps now we can borrow ideas from quantum fluids, to build minicomputers from biological cells,” Fakhri says.

The research is described in Nature Physics.

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Physics in the pandemic: ‘My workplace probably looks more like a war zone now’ - Physics World

On Thursday 12 March I went back to school to give a talk as part of British Science Week. The message I tried to convey to the audience of 10-year-old children was simple: to keep healthy, it is important to have a healthy lifestyle and exercise regularly. If they did not get why back then, I am sure they will by the end of this pandemic!

That was only one week before schools were shut down in the UK and the government recommended to all of those who could do to work from home. Our university had preceded them by asking non-clinical staff not to come to St Thomas’ Hospital, the central London hospital where I work that also treats many patients. As our head of school stated, being fully embedded within the hospital offers a fantastic environment for research, but can present additional health risks in times like these.

To be fair, there was a slow build up to this and we had seen it coming. First were the pods I noticed one day right outside the hospital entrance on my way to meetings with my supervisors. It turned out these were where suspected COVID-19 patients would go first to avoid entering the hospital premises and potentially contaminate other people. There were the students I met in the lift while I knew they should be having a tutorial I used to teach. They said that they thought it had been cancelled. But the strongest hint was when one of my supervisors asked to schedule our next few meetings on Skype, as the school would probably be closing soon. Two hours later we all received the e-mail from our head of school.

So ever since, I have been working from home while trying to stay away from the news as much as possible. I still saw the ExCeL centre in East London, where I helped my school to present a New Scientist Live stand on the future of surgery last October, get turned into the NHS Nightingale Hospital London. As for the hospital I work in, where Florence Nightingale established the first professional nursing school in the world, it probably looks more like a war zone now than a workplace…

My work is highly interdisciplinary, ranging from designing new technologies to help clinicians assessing cardiovascular status, to gaining more fundamental understandings of hypertension, and a lot of it depends on collaborations with clinicians and doctors. Since the beginning of the outbreak, all cardiovascular MRI scans in my hospital have been cancelled, putting on hold most of the clinical studies I am involved in. Similarly, I haven’t heard from some clinical supervisors and collaborators, who I assume have been requisitioned or have volunteered to help. I am trying to finish the papers and software I was working on, hoping that they can add their parts and insights later. I also communicate with my engineering supervisor and am watching out for ways to help.

In the meantime, as countries are being shut down and borders drawn up, some of us have had to make a choice: staying in London or going back home. It got to the point where my dad back in France asked me whether I preferred to be treated in France or in the UK should I get the virus. I decided to stay, thinking I would probably feel more useful here, but some of my colleagues decided to go back to Mexico or India. Others are facing the prospect of taking their PhD viva online, dealing with cell culture problems or juggling working from home with having to care for children or elder relatives.

I think research, like so many aspects of our lives, will come through deeply transformed from the current situation. For example, the collaborative environment between research groups is amazing, be they working on the virus or on engineering solutions to help clinical staff on the frontline. I am also pleased by the focus on the importance of science in decision making and engineering in healthcare. These are for me a cause for optimism moving forward!

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Life in a carbon-neutral world - Physics World

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Green footprint
(Courtesy:iStock/Griffin24)

I live in the UK city of York and in March 2019 it declared a climate emergency, with the city’s council agreeing to become net carbon neutral by 2030. It was a bold declaration and an ambitious target. But York is far from alone in taking such a stand – more than 70 countries and hundreds of cities have now pledged to reduce carbon emissions to net zero by 2050 or sooner. Some countries, including the UK, have even turned this into a legally binding target. Right now, there is lots of discussion about how we might reach net zero, but what will it feel like to live in this clean, green world?

Like many others, in pre-COVID-19 times, I drove my car to the supermarket, went to work in a draughty office, heated my home with gas central heating, ate meat a couple of times each week, and liked to go somewhere warm for a holiday each year. Over the last few years I’ve made a few changes to my life to cut my own carbon footprint – taking the train instead of flying; trying to cycle more, instead of driving; eating less meat and dairy; and putting on another jumper instead of turning the thermostat up. But I’ve got a long way to go before I fully neutralize that footprint. However, if my hometown manages to keep its pledge, I’ll be living in a net-zero city in just 10 years’ time, and once my children are grown-up we’ll be living in a carbon-neutral country.

Currently, the UK government believes that we’ll have to use carbon-capture-and-storage technology to reach our targets. If we go down that route, then net-zero living may not feel too different to life today (see box below). But burying our emissions isn’t the only option. A forthcoming report from the Centre for Research into Energy Demand Solutions (CREDS) explores an alternative path based on radical reduction in energy demand. Meanwhile, Cambridgeshire County Council recently published Net Zero Cambridgeshire, which plots a more middle-of-the-road path by proposing both decreasing energy usage, and using carbon-capture-and-storage technology to reach net zero. Last November UK FIRES (a research collaboration between five UK universities) published Absolute Zero – a report detailing how the UK might completely eliminate all its greenhouse-gas emissions by 2050.

The technological fix

Peatland Wicken Fen UK
A natural solution: Wicken Fen in Cambridgeshire is a historic peatland that has been undergoing restoration since 1999. (Courtesy: Shutterstock/Andy333)

One way of slowing climate change is to take the offending greenhouse gases out of the air. Natural solutions include planting trees and restoring peatlands, while the main technological contender is carbon capture and storage (CCS) – gathering carbon dioxide from a power station, for example, and pumping it into an underground storage area. The UK is well placed to take advantage of CCS. “Our oil and gas industry has left us with many suitable reservoirs under the North Sea – enough to store 100 to 200 years’ worth of emissions for the UK,” says Stuart Haszeldine, a CCS expert at the University of Edinburgh. The carbon dioxide would remain locked underground for tens of thousands of years, buying us more time to bring emissions down.

If we do embrace this route to net zero, then Haszeldine envisages hydrogen being the fuel of choice for heating our homes (using the existing gas network), and electric and biofuels meeting many other energy needs. As for food, meat will stay on the menu, but might be lab-grown rather than from the farm. Life will feel a bit different, but not radically different from today.

However, Haszeldine is clear that CCS is not an excuse to slack off. “We still need to do everything we can to decrease emissions, but CCS is our insurance policy. It’s worth doing multiple actions in case some fail.”

Bringing it home

Like many other cities in the UK, a significant chunk of York’s greenhouse-gas emissions – around a third in fact – come from heating and powering our houses. Reducing energy use at home is going to be a crucial aspect of reaching net zero. “When it comes to homes we are going to have to phase out carbon-based heating,” says James Weber, a climate scientist at the University of Cambridge and one of the authors of Net Zero Cambridgeshire.

So that’s goodbye gas and hello low-carbon heat sources such as heat pumps, photovoltaics and smart energy-storage systems. But eco-energy alone won’t be enough; extensive improvements in energy efficiency are needed too. Indeed, the CREDS team calculates that we can halve our domestic energy demand so long as two-thirds of UK homes become super-insulated and have their gas boilers replaced within the next 15 years.

It’s goodbye gas and hello low-carbon heat sources. But eco-energy alone won’t be enough; extensive improvements in energy efficiency are needed too

It sounds like a serious undertaking, but some people have already embraced the challenge. Phil Bixby, a York-based architect, has retrofitted his end-of-terrace Victorian brick house to be super-energy efficient. “I didn’t do this to be an eco-warrior; I did it because it seemed the responsible thing to do and I wanted to show that you don’t have to forgo comfort to do this,” he says.

Superficially, the interior of Bixby’s house looks like any other home, but closer inspection reveals otherwise. Leading me over to the window during my visit in January, Bixby points out the additional 12 cm or so of insulation that has been added to the exterior walls. He chose high-performance polyurethene – a commonly used insulation material – over natural fibres such as sheep’s wool or hemp because it is more efficient, requiring less material, and hence wall thickness, for the same level of insulation. Looking around I also realize that there are no radiators; three electric towel rails and a small area of underfloor heating is the only additional warmth the house needs. To prevent condensation, a mechanical ventilation system extracts damp air and pulls in fresh air to all the living spaces. Meanwhile, in the dining room, positioned in pride of place, is a Tesla battery unit, which stores any excess electricity generated by the building’s solar panels and pulls electricity from the grid when extra is needed. Using weather-forecast data, it optimizes capturing solar energy on sunny days, and buys electricity when it is cheapest, helping to smooth the National Grid’s load.

The house doesn’t achieve official “Passivhaus” standards – where heat loss is reduced so much that the building hardly needs any heating at all – but it isn’t far off. “Our energy bills are around £700 per year now; approximately half of what they used to be,” says Bixby. And cheaper energy bills are not the only benefit. The filtered air helps prevent respiratory problems and the thick walls make it super quiet.

Energy-efficient home
Modernizing history: Whether it’s a Victorian terraced house (such as Phil Bixby’s home in York, above) or a former brewery (such as Resource Rows in Copenhagen, below), retrofitting existing buildings to become energy-efficient homes uses less carbon dioxide than building new houses. (Courtesy: Phil Bixby)
Resource Rows in Copenhagen
(Courtesy: Mikkel Strange)

Retrofits like Bixby’s don’t come cheap, but they could play a role in solving the UK’s housing crisis. The government’s target is to build 300,000 new homes every year by the mid-2020s, but the CREDS team says that repurposing empty homes could reduce the number of new-builds to under 200,000 every year, and breathe new life back into small towns, where many of the empty homes lie. “Building a new home can emit around 70 tonnes of carbon dioxide – approximately 15 return flights from the UK to Australia,” says John Barrett from the Sustainability Research Institute at the University of Leeds, UK, and co-ordinator of the forthcoming CREDS report. Around half the embedded energy in a building lies in the concrete and steel, so repurposing rather than demolishing can significantly reduce emissions.

Some architects are already embracing this philosophy. In the Danish city of Copenhagen, for example, architect Anders Lendager’s recent housing development, called Resource Rows, reused panels of brickwork from the demolition of a Carlsberg brewery building, halving carbon-dioxide emissions compared to conventional construction. And less flashy but equally impressive is the refurbished Minerva building in Leeds, which reused the existing concrete and steel frame of its 1970s predecessor to create a modern and energy-efficient office building.

Travelling with no footprint

So far, so good, but an eco-home can only get you so far. How do we tackle another huge source of emissions: transport? Where I live in York, vehicles are responsible for another third of the city’s greenhouse-gas emissions. It’s a similar picture across the rest of the country and a difficult one to fix. Electric vehicles will play a role, but they don’t solve congestion and still emit particulate matter from road, tyre and brake wear. Indeed, if everyone goes electric the demand for electricity will be huge. Switching to other modes of transport, and travelling less, are going to be important too.

In its report, Cambridgeshire County Council estimates that 10% of the distances we travel by car will have to be done using public transport, walking and cycling. The CREDS team goes even further than this and suggests that it’s plausible to halve the number of trips we take by car and reduce our number of car miles by 20%. For shorter journeys, walking and cycling will play a big role, making up 40% of our journeys (as compared to 25% now). UK FIRES presents the most radical change, with shipping significantly reduced and most airports closing this decade, leading to absolutely no shipping or air travel by 2050. But some don’t see this solution as wholly realistic. “I feel that this scenario fails to take into account the speed of social change and the potential damage associated with completely stopping world trade,” says Barrett.

For most of us, though, the biggest change we’ll notice will be the way we travel to work. “Commuting traffic generates the largest proportion of greenhouse-gas emissions but it is also the most difficult thing to change. We can’t rebuild our cities from scratch,” says Marc Barthelemy, an expert on spatial networks at the CEA Institute for Theoretical Physics in Saclay, France. Barthelemy has analysed traffic data from 25 major cities and showed that cities that combine high-density living with good access to public transport have the least traffic congestion and the lowest transport-related emissions. “In Tokyo, Seoul and Barcelona around 80% of the population live within 1 km of public transport and the percentage of people using their car in these cities is very low,” says Barthelemy. But counterintuitively not all public transport is a good thing. Barthelemy’s work has shown that public transport stations in outer suburbs can encourage car use and add to traffic congestion in the vicinity of the station. “Things like ‘park & ride’ are the wrong solution. They enable people to live further away from the city and encourage longer commutes,” he explains.

Things like ‘park & ride’ are the wrong solution. They enable people to live further away from the city and encourage longer commutes

Instead of focusing on extending subways and building “park & rides”, Barthelemy thinks that cities dominated by urban sprawl – such as Dallas and Los Angeles in the US – need to incentivize “urban villages”, where offices, homes and shops are mixed together. “You can already see this happening in cities like Dublin [Ireland], where big companies such as Google and Facebook have set themselves up outside of the city centre and are in the process of creating a nice living environment around them so that employees are encouraged to live their lives nearby,” says Barthelemy.

One city that has managed to bring about a fast change in people’s transport habits is Ghent in Belgium. The city transformed overnight on 3 April 2017, when it was divided into seven distinct transport zones – a car-free area in the historic centre with six zones radiating out from it like petals on a flower. “We made it impossible to go by car from one zone to another, but for pedestrians, cyclists, taxis and buses nothing changed,” explains Filip Watteeuw, the deputy mayor of Ghent, responsible for implementing the plan. “People started to question whether it was necessary to take the car and we quickly saw a big shift towards public transport and walking and cycling.”

In the three years since Ghent’s traffic plan was implemented, the number of traffic accidents has fallen by a third, the number of cars has dropped by a third, cycling has increased by 60%, carbon-dioxide emissions have been slashed by 1500 tonnes per year and there has been a significant improvement in air quality. Many people predicted that business would suffer, but in fact Ghent has seen a rise in start-ups and even a limited decrease in vacant shops. “The economy is good,” says Watteeuw. And because the plan simply repurposed existing roads, rather than building new infrastructure, it cost just 6m to implement – about the same cost as building one mile of motorway. But for Watteeuw it is the improvement in people’s quality of life that he is most proud of. “The most lovely compliment I had was from someone who said I was the best musical composer, because now they can hear the songs of the birds and before they could only hear the noise of cars,” he says. Birmingham – the UK’s second-biggest city – is already eyeing up a similar plan.

Work patterns will also need to change in order to accommodate reduced travel, and Barrett predicts greater flexibility from employers, with co-working hubs, home working and virtual meetings all becoming the norm. The COVID-19 virus has forced us to rapidly embrace many of these practices. But what kind of jobs will we be doing in a net-zero world? The fossil-fuel industry will become near-obsolete, but other opportunities will arise. “We anticipate a growth in renewable-energy industries and the IT sector, plus a rise in demand for people with engineering skills as we embrace a culture of recycling and repairing,” says Barrett. Builders and heating engineers will be run off their feet retrofitting everyone’s homes.

One important aspect of the CREDS scenario is a big reduction in the amount of stuff we buy, with throwaway fashion a thing of the past. The average lifetime of materials will increase by two years and changes in design standards will make products easier to repair. “The emphasis needs to change to value quality over quantity, and when something does break, we’ll be able to send it back to the manufacturer or take it to a repair cafe in the town centre,” says Barrett. Mundane shopping will be done online, out-of-town shopping malls will disappear, and a trip to the town centre will be a leisure experience, to have a coffee with friends or visit an attraction.

Eating in a net-zero world

So that’s transport, energy, work and leisure mapped out, but what about food? York hasn’t included food in its emissions tally, but the impact of agriculture is estimated to make up around 10% of global greenhouse emissions. Ruminants such as cows and sheep take much of the blame because they produce significant quantities of methane – a short-lived but very potent greenhouse gas. Will beef, lamb and dairy products still be on the menu in a carbon-neutral world?

Under the CREDS scenario, 40% of the UK population will be vegan (up from 3% today) and 40% will be vegetarian (up from 9% today). “We envisage a large shift in people’s diet. It will still meet all our nutritional requirements, but we’ll see a big reduction in the number of calories we consume,” says Barrett. One significant co-benefit of this shift is the improvement in people’s health, with obesity being eliminated (65% of people are classified as overweight or obese in the UK today).

However, Michelle Cain from the Environmental Change Institute at the University of Oxford, UK, suggests we might not need such a radical change in diet. Her work has shown that the short-term positive benefits of reducing methane levels are greater than often assumed and that even small changes could have tangible benefits. For example, the impact on climate of a cow herd occurs when it is first established, and remains steady over time if the herd remains the same size because the effect of methane is short lived. Cain’s calculations show that reducing methane emissions from a herd by 0.3% per year – either by decreasing herd size or by using feed additives and improved manure management – is enough to bring the emissions of the herd down to net zero. “Our calculations suggest that this reduction will have the same impact on climate as closing and stopping the carbon-dioxide emissions from an entire coal-fired power station,” says Cain.

Whichever route we choose – vegan, vegetarian or flexitarian – a walk in the countryside is going to feel very different in the decades to come. “Fewer fields of livestock will free up land and create opportunity to capture carbon by planting trees and restoring peatland,” says Barrett.

Both CREDS and Net Zero Cambridgeshire rely on trees in a big way. Weber and his colleagues calculate that even with all their proposed energy-reduction measures in place, Cambridgeshire will produce an excess 600,000 tonnes of carbon during the year 2050. Planting 0.5% of the county with trees now would be enough to mop up that much carbon between now and 2050, thereby ensuring Cambridgeshire hits the net-zero target in 2050, but it wouldn’t tackle the excess emissions produced between now and then, or those produced from 2051 onwards. If we want to hit net-zero by 2050 and maintain net-zero thereafter, they calculate that a whopping 10% of the county’s land area needs to be planted with trees now. As an added bonus, reforesting on this grand scale would also lock away around 10% of the county’s emissions in the lead-up to 2050, helping Cambridgeshire to reduce its contribution to global warming from the moment the trees are planted. But not just any old tree will do. “It is important that this isn’t a monoculture because that makes the trees vulnerable to disease and is bad for biodiversity,” says Weber. Instead the team concludes that most of the planting needs to be a mix of alder, aspen and sycamore, to maximize carbon sequestration, interspersed with a smattering of commercial forestry and traditional woodland.

Cambridgeshire will also need to restore peatland to turn it back into a carbon sink. “North Cambridgeshire has large areas of peatland that have been disturbed and used as farmland. If this peatland continues to degrade it will become a major source of emissions,” says Weber.

Bo Asmus Kjeldgaard
Making changes: Bo Asmus Kjeldgaard, former mayor of Copenhagen, believes that working collaboratively with stakeholders is key to the major projects required to achieve zero-carbon cities. (Courtesy: Greenovation)

Certainly, life is going to be very different in a net-zero world, but it’s far from the hair-shirt and lentil-eating existence that I might have imagined. And, if Copenhagen is anything to go by, net-zero living could be positively rosy. Back in 2009 the city set itself the goal of becoming carbon neutral by 2025. With five years to go, the city is pretty much on track, having reduced its emissions by 42% over the last 15 years, while growing its economy by 25%. Today two-thirds of trips in the city are made on foot, cycle or public transport, and more than half of the city’s heat and power is supplied by renewable energy. “We were motivated by wanting to improve the ‘liveability’ of the city, to combine sustainability and good quality of life,” says Bo Asmus Kjeldgaard, former mayor of the city and now chief executive of sustainable consultancy Greenovation.

But getting here has required tough decisions and significant investment. “Back in the 1990s we made it mandatory to connect to Copenhagen’s district heating system. Lots of people were against this but we knew we had to connect everyone to get the full benefit,” says Kjeldgaard. Ownership of utilities companies was also important, to ensure the city had control of its own power. However, it hasn’t all been top-down decision making, and Kjeldgaard is clear that working collaboratively with all stakeholders and gaining the trust of local people have been crucial too (see box below).

Kjeldgaard is also well aware that the city has not addressed the emissions associated with air travel, what people eat or what they choose to buy. “This wasn’t part of our calculation because we can’t control this, but we should be calculating these emissions and informing people about the choices they make,” he says. Kjeldgaard thinks there are still big challenges ahead for Copenhagen, but he is pleased that the city has demonstrated what can be achieved with good planning. “It hasn’t been like going back to the old times. We’ve shown that you can still be modern, use your computer, live in a nice home and eat inventive food, but also enjoy clean air and nature in the city,” he says. And if that is what is on offer, I’ll have a slice of that.

Governance for a carbon-neutral world

Ghent transport
Neutral transport: Ghent has achieved impressive reduction in car use since 2017. (Courtesy: CC BY 2.0/bvi4092)

Whichever the route, the journey to net zero it is a daunting challenge. So where do we begin? Beth Sawin, co-director of the US think-tank Climate Interactive, thinks that we need to start by implementing solutions that solve more than one problem – a technique she calls “multi-solving”. “For example, if we make walking and cycling safer, it helps to reduce air pollution and traffic congestion, and improve people’s health,” she explains.

But the convention of allocating budgets to specific government and council departments doesn’t favour multi-solving, with the transport department, say, spending money on cycle paths but failing to get the credit for the health savings, for example. “We need to connect decision-makers across different departments and allow them to take the whole system into account. Cities with mayors are often better able to do this,” says Sawin.

But that doesn’t mean we need to wait for a mayor to come along. Sawin has been involved in a number of successful multi-solving projects, where the wisdom and desires of the groups of people with most at stake are incorporated into the decision-making process. One such collaboration in the US city of Atlanta, known as the Just Growth Circle, brought together almost 70 people including representatives from government, business, philanthropy, conservation and local community groups. Over time the group members have come to trust each other, and worked together to shape an urban restoration plan, creating parks, walking trails and clean rivers, but also securing commitments to protect against gentrification of the neighbourhood. “Because these groups of people are already connected, they are able to seize opportunities when they arise, and steer towards outcomes like equity, climate protection and health,” says Sawin.

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Europe seeks to harness power of AI in COVID-19 crisis - Physics World

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© AuntMinnieEurope.com
© AuntMinnieEurope.com

Artificial intelligence (AI) may soon have a central role to play in the global battle against COVID-19. A European campaign is underway to develop a deep learning-based model for the automated detection of abnormalities on chest CT and for quantifying lung involvement.

“In these unprecedented circumstances, we must find ways of helping doctors in their fight against the virus,” noted Erik Ranschaert, president of the European Society of Medical Imaging Informatics (EuSoMII), who is leading the initiative with fellow radiologist Laurens Topff, from the Netherlands Cancer Institute (NKI) in Amsterdam. “The value of AI also comes into play, by reducing the burden on clinicians. While a manual read of a CT scan can take up to 15 minutes, AI can finish reading the image in 10 seconds.”

Around 30 partners have already expressed their willingness to share data and to support the plan to train the algorithm. These include academic and non-academic hospitals located in the most affected areas of Italy and Spain, and also in Germany, Belgium, the Netherlands and the UK.

European hospital collaboration
The map shows the European hospitals collaborating in the COVID-19 project, as of 20 March. (Courtesy: Erik Ranschaert)

Each hospital will transfer the data directly and securely to the servers of Quibim. Based in Valencia, Spain, it specializes in machine learning and image processing technologies for medical images, and it will provide a research platform for the development and deployment of the deep-learning model. For data preparation, annotation and algorithm training, the Robovision AI (RVAI) software will be used. The data will only be used for research purposes.

Automated image analysis with AI techniques can optimize the role of CT in the assessment of COVID-19 by supporting clinical decision-making, improving workflow efficiency, and allowing accurate and fast diagnosis of infection in a large number of patients, Ranschaert explained.

“We believe that it’s possible to train an accurate AI algorithm with the wealth of data already available since the outbreak of the virus in Europe, with the main aim of helping doctors to make this diagnosis in time,” he added.

A team from the NKI will assess and statistically analyse the performance of the deep-learning model, which will be made freely available as a research solution to participating hospitals.

Growing use of CT

The clinical presentation of patients with COVID-19 ranges from asymptomatic to severe pulmonary infection. The most specific method and reference standard to diagnose infection is the reverse transcription polymerase chain reaction (RT-PCR) test, but due to the varying levels of sensitivity of viral testing, shortage of viral testing kits and longer turnaround times to provide results, lung CT scans are attracting attention, Ranschaert said.

“COVID-19 causes a wide variety of findings on these scans, most typically ground-glass type of densities located on the outside of both lungs (see white areas in figure),” he continued. “The accuracy of chest CT to diagnose COVID-19 has been reported as high and can predate a positive classic serological RT-PCR test. Therefore, in endemic areas where the healthcare system is under pressure, hospitals with a high volume of admissions are using CT for rapid triage of patients.”

CT scan of a COVID-19 patient
CT scan of a COVID-19 patient who was originally referred for CT angiography of the chest to exclude pulmonary embolism. (Courtesy: Erik Ranschaert)

There is a role for chest CT to assess COVID-19 infection in patients with severe and worsening respiratory disorders. Based on the images, doctors can evaluate how severely the lungs are affected and how the patient’s disease is evolving, which is helpful in making treatment decisions, according to Ranschaert.

Also, pulmonary abnormalities caused by COVID-19 can be found by chance in exams carried out for other reasons – for example, abdominal CT scans for bowel problems – in patients without respiratory complaints.

“Patients are coming in with different types of complaints and therefore sometimes get other examinations. Some radiologists are even proposing to do a standard CT chest with every CT abdomen,” he noted. “If a CT abdomen needs to be done because of nonspecific complaints, just scan higher to assess more lung tissue, leading to more nonspecific COVID-19 patients being detected.”

In areas of widespread coronavirus outbreak, many hospitals are installing special scanning units to enable efficient screening of the steadily growing number of victims. If CT is used for screening, there will be so many studies that radiologists will be overwhelmed and AI will be urgently needed.

“The scans run full-time and the number of doctors to assess all these scans is sometimes insufficient, partly due to the fact that doctors are also more often exposed to infected patients and therefore themselves become victims of the virus,” Ranschaert pointed out, adding that 300 Chinese doctors had to be flown into Italy to cope with the growing number of patients.

The danger of cross-infection via the CT scanner is an important consideration.

“Some hospitals are very prudent and do a complete disinfection of the CT scan suite, taking about an hour,” he said. “Others only clean the contact surfaces of the scanner, while also protecting the radiographers of course with an adapted outfit – this on advice of their microbiologists. These hospitals usually have a dedicated scanning suite for COVID-19 scans. Some even have a mobile unit outside the hospital to provide these scans.”

A LinkedIn post last week was viewed more than 100,000 times with over 2000 likes. The website for the project is active now.

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A Decade of Discovery Enabled by PeakForce Tapping - Physics World

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PeakForce Tapping has been widely adopted in a broad range of research fields, outpacing all other recently developed AFM modes in research impact and productivity.

Webinar Overview
In December 2009, a new mode for atomic force microscopy was introduced – PeakForce Tapping. Since then, it has been widely adopted in a broad range of research fields, outpacing all other recently developed AFM modes in research impact and productivity. PeakForce Tapping and its associated modes ScanAsyst, PeakForce QNM, PeakForce TUNA, PeakForce KPFM, and PeakForce SECM, have been cited in more than 4000 peer-reviewed publications over the last 10 years, with more than 30% of these publications in the top 10% of journals. In this webinar, we will select from this vast repository of publications to review the impact of PeakForce Tapping on today’s science. In particular, we will examine how the measurement of mechanical and electrical properties at the nanoscale have led to new discoveries and insights into material behavior.

PeakForce Tapping eliminates the need for contact mode in electrical modes, such as conductive and tunneling AFM (e.g. PeakForce TUNA), allowing high-resolution electrical property maps even on soft and fragile samples, and even in liquid (with PeakForce SECM). Battery work using the mode includes a recent Nature Communications article co-authored by Professor John Bannister Goodenough, the 2019 Chemistry Nobel laureate, where high-performance, dendrite-free metal lithium anodes were characterized. In energy research, PeakForce Tapping studies have resolved conductivity along individual lamellae in organic photovoltaics, revealed a nanocontact pinch-off that allows for improved solar fuel devices, and characterized the SEI layer in Li ion batteries in operando as well as ex situ.

Since PeakForce Tapping provides piconewton-level force control and sensitivity, it is ideal for mapping the nanomechanical properties of materials (enabling a mode called PeakForce QNM). Among the many firsts enabled by PeakForce QNM is work by Professor Konstantin Novoselov and Professor Andre Geim, the 2010 Physics Nobel laureates for the discovery of graphene, revealing a commensurate–incommensurate state transition in graphene on boron nitride, as shown in their Nature Physics article. In biology, it has enabled new studies of ligand receptor interactions, of individual microvilli on live cells, and of variations in the DNA double helix structure, to name just a few. In studies of polymers and composites, it has become the mode of choice for quantifying properties at interfaces and in interphases, including in adhesives, where other AFM modes struggle.

 

Bede Pittenger, Ph.D. vita:
Dr. Bede Pittenger is a senior staff development scientist in the AFM Unit of Bruker’s Nano Surfaces business. He received his Ph.D. in physics from the University of Washington (Seattle, WA) in 2000 and has worked with scanning probe microscopes for 25 years, building systems, developing techniques, and studying properties of materials at the nanoscale. His work includes more than 30 publications and four patents on various techniques and applications of scanning probe microscopy. Dr. Pittenger’s interests span topics from interfacial melting of ice, to mechanobiology of cells and tissues, to the nanomechanics of polymers and composites.

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Physics in the pandemic: ‘My job is not amenable to working from home’ - Physics World

Photo of an optical setup bathed in purplish light
Making lasers behave As in most atomic physics experiments, the equipment in Hannah Williams’ lab requires regular attention and cannot be operated remotely. (Courtesy: Hannah Williams)

I moved to France with my partner just over five months ago, and we now live in a small flat in the centre of Paris. As an experimentalist, I usually spend most of my day in the lab, often coaxing the lasers into behaving. In my experiment, we trap individual atoms in an arbitrarily arrangeable array of optical tweezer traps. We can then excite these atoms into a Rydberg state and use the set-up to simulate quantum systems. There is no such thing as a normal day for me, as my tasks are dictated by the current state of the experiment. Over the course of a week I could be working on a laser, taking data, analysing and writing up results, or fixing machinery or other pieces of equipment. This hands-on variety is my favourite part of being a researcher.

Empty shops, empty lab

As with most people, the pandemic has had a huge impact on my daily life. The French government closed universities and research labs on 13 March, and since then it has introduced strict lockdown rules. My partner and I are expected to stay in our apartment, only leaving for food, medicine or exercise. We must remain within 1 km of our home, return within an hour and carry a note indicating the time we went out and the reason why. From my brief excursions it seems like people are adhering to these rules; the streets are empty and the shops and hotels have been boarded up, although the boulangeries remain open to provide the city with baguettes and croissants. This lockdown was initially set to last for 14 days, but it is likely to be extended.

The vast majority of my job is not amenable to working from home. Sadly, the experiment consists of many physical buttons and switches that need pressing in order to run, and it cannot be controlled remotely. Therefore, I have had to find new tasks that can be completed from the (relative) comfort of my dining table. I am currently focusing on building and running simulations of the experiment. This is a good task for me as I have wanted to do this for a while, but I find it too easy to get distracted by the goings-on in the lab.

Three mornings a week the lab has a group Skype where we discuss our work, catch up and check in on one another. Last week I also took part in a workshop that had been moved online. I had not registered for the “real-life” version, and had it not been for the global lockdown I would not have known about it. I also might never have got to experience being totally confused by a theory talk while sitting on my sofa, in my joggers.

A photo of the Pantheon, a large Classical building with columns and a dome with the French tricolour on top and an empty plaza out front
Deserted The Pantheon in Paris is normally a major tourist destination, both in its own right and because it has an uninterrupted view of the Eiffel tower. (Courtesy: Hannah Williams)

Blue skies above, anxiety below

Staying inside my flat has not been easy, as I like being outside and walking. I usually walk for over an hour each day just to get to my lab, but my Fitbit informs me that last week I walked 50 km less than normal. To make matters worse, the weather in Paris is suddenly beautiful, with blue skies every day and temperatures warm enough to eat ice-cream in the street. However, I understand the importance of staying inside and I know that I am in a position of privilege; I am healthy, I’m still getting paid, I live with my partner and French supermarkets are being kept very well stocked. I am enjoying the extra time I have because I’m no longer commuting; I am cooking more, doing yoga (almost) every day and running three or four times a week. I am also talking more to friends and families via group Skypes and virtual pub meet-ups in which we try to avoid talking about the virus, but inevitably circle back round to it.

I miss the lab, and I miss the work I was doing. After five months in my role, I finally really understood the experiment and was very excited about the data we were taking. Some days are harder than others and remaining productive can be a challenge. I feel anxious about the health of family and friends and down about the state of the world. It is difficult to escape from the barrage of statistics and endless lists of “How to be productive at home”, “Best workouts to do in your living room” and “Top TV shows to binge watch” – none of which make for interesting or uplifting reading. This is a time of uncertainty and disruption which many of us have never faced before, with no clear end in sight. So when I feel anxiety or stress, I take a break. I don’t try to make myself work. I do something else – and above all, I get off the Internet.

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Nanoscale structures give some butterflies ‘ultra-black’ wings - Physics World

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Many male butterflies have exceptionally black wings with optical properties that have long-puzzled scientists. Now researchers in the US found that the wings of at least ten species have nanoscale structures that increase light absorption and scattering that create the “ultra-black” appearance. These structures may have evolved to enhance the contrast of colour patches used in courtship displays, according to the researchers. Understanding why the wings are so dark could lead to the development of ultra-black synthetic materials.

Butterfly wings are made of scales that usually consist of two chitin layers. One layer is a smooth, flat plate. The other layer has ridges that are connected by cross ribs to form a honeycomb-like structure. The two layers are connected by pillars known as trabeculae.

It has been suggested that the size of the nanoscale holes in the honeycomb-like structure on the upper scales could be responsible for the extreme light-absorbing properties of some butterflies. But when Alex Davis at Duke University and colleagues examined the scales of ten butterfly species that are exceptionally black, they found that that was not the case.

Extremely low directional reflectance

When the researchers shone light on specimens from museum and university collections, they found that the black scales had an extremely low directional reflectance. With the light source perpendicular to a wing’s surface, the ultra-black butterflies only reflected between 0.06-0.4% of light, they report in  Nature Communications. In contrast, “control” butterflies that are brown or less black, had reflectance values between 1-3%.

Scanning electron microscopy on both the ultra-black and control butterflies found, however, that there was considerable variation in the shape and size of the holes in the upper wing scales – with them ranging from honeycombs and rectangles to a V-shaped pattern. The ultra-black specimens covered four different subfamilies of butterflies and there was little similarity between the hole structures. This led the researchers to conclude that hole shape or size is not linked to ultra-blackness.

Instead, Davis and colleagues found that other structures were very similar across the ultra-black specimens. The parallel ridges and trabeculae on their wing scales were much deeper and thicker than in the control butterflies, which had larger gaps between the ridges and either no or significantly reduced trabeculae.

Computer models

Next the team created computer models of different wing scales. Simulations of scales without either the ridged surface or interior pillars reflected up to 16 times more light, while those lacking both were up to 28 times more reflective.

Davis told Physics World that expanded trabeculae and ridges, the ultra-black butterflies have more surface area for absorbing and scattering light. This combined with the light absorbing pigment melanin, which is embedded in the structure, produces the low reflectance. Light enters the scales and bounces around, but very little bounces back.

This structure is so good at absorbing light that the ultra-black scales still appear black when coated with gold for scanning electron microscopy, the researchers report.

Brightly coloured areas

Ultra-black wing patches in butterflies often border brightly coloured areas. The researchers believe that the black patches have evolved to make those colours appear brighter during courtship. “Given that the males are much blacker than the females in most of these species, we suspect ultra-black scales have evolved to increase the contrast of signals used in mating,” Davies explains. “These butterflies tend to court one another in sunny areas where a typical black scale may look washed out.”  Davies thinks there are probably many other ultra-black butterflies using the same structures.

Silvia Vignolini at the University of Cambridge, who was not involved in the work, thinks there could be a more functional benefit to the enhanced light absorption. “They need to warm up the wings in order to fly,” she explains.

Vignolini adds that the study is interesting because it compares different butterfly species and families and shows how scale morphology can decrease reflection. She cautions, however, that while she sees no reason to doubt the results, the paper lacks detail on how the authors measured reflectance, and what they measured.

It is also not safe to assume that a single, ultrathin (2.5 μm) scale from one of these butterflies would show the same levels of reflectance, Vignolini says, as the researchers studied whole wings. “The wing is composed of more than one scale, and the scales are superimposed on top of each other,” she says. Adding that this means that “you have more scattering, because you have space between each scale”.

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Beating COVID-19: the April 2020 issue of Physics World is now out - Physics World

Physics World April 2020 cover
Life in the pandemic: how physics is helping us understand the virus behind COVID-19.

Like everyone else around the world, physicists have been caught up in the COVID-19 outbreak, which was declared a pandemic by the World Health Organization last month. Naturally, all of us will be concerned first and foremost for our own friends and family.

The disease is usually mild, but it can turn nasty – and with lots of people falling ill at once, there will be big pressures on medical systems around the world. It goes without saying that we should all look out for each other, especially older neighbours, colleagues and family members.

And with so many of us under lock-down, what better time to sit back with the latest issue of your favourite physics magazine, now out in print and via the Physics World digital apps for iOSAndroid and Web browsers.

The cover feature is by science writer Jon Cartwright, who looks at how physics-based techniques are helping us to understand the virus behind COVID-19 – also available online here.

We’ve created a short video that summarizes the key points: bottom line, we can thank X-ray crystallography, cryo-electron microscopy and network theory for understanding the disease and how it spreads.

Remember that if you’re a member of the Institute of Physics, you can read the whole of Physics World magazine every month via our digital apps for iOSAndroid and Web browsers. Let us know what you think about the issue on TwitterFacebook or by e-mailing us at pwld@ioppublishing.org.

For the record, here’s a rundown of what else is in the issue.

• Coronavirus puts physics in turmoil – COVID-19 has hit the international physics community hard, with meetings and conferences cancelled, including the showpiece events of the American Physical Society. Matin Durrani surveys the fall-out from the global pandemic.

• Moving forward together – In the run-up to a pivotal announcement on the future of particle physics in Europe, Tessa Charles urges backers of rival colliders to unite around whichever project gets the go-ahead.

• What would you do? – Robert P Crease examines his responsibility for not exploring one physicist’s treatment of women.

• Shipping carbon-free – Air travel is bad for the environment – but shipping is not that great either. James McKenzie wonders how best to decarbonize sea travel.

Fighting a pandemic – The latest novel coronavirus, SARS-CoV-2, has reached pandemic status. While health workers and governments do their part, scientists are trying to understand the virus and develop vaccines and treatments. Jon Cartwright looks at how physics plays an important role in the fight.

• Life in a carbon-neutral world –Increasing numbers of cities and countries around the globe are pledging to become net carbon neutral within the next few decades. But what will day-to-day life look like in a “net-zero” world? Kate Ravilious looks at the changes that society will need to make.

• The diamond quantum revolution – Diamond is more than just a pretty gem – it has many attractive properties that stretch far beyond its aesthetic appeal. Matthew Markham and Daniel Twitchen from UK firm Element Six explain how this special form of carbon now has many practical quantum applications too.

• Can a machine think? – Susan Curtis reviews The Road to Conscious Machines: the Story of AI by Michael Wooldridge.

• Duck, duck, goose? – Ian Randall reviews At the Edge of Time: Exploring the Mysteries of Our Universe’s First Seconds by Dan Hooper.

• Half a life – Jess Wade reviews the film Radioactive, a biopic about Marie Curie directed by Marjane Satrapi, screenplay by Jack Thorne.

• Going with the flow – Early-career industry physicist Aidan White tells Joe McEntee about his work as a project engineer at TÜV SÜD National Engineering Laboratory, the UK’s designated institute for flow and density measurement.

• Ask me anything – In the latest in our new series of careers-advice articles, we feature Chad Orzel, who is an associate professor in the Department of Physics and Astronomy at Union, and author of four popular-science books.

• Physics on ice – Rhett Allain uses simple Newtonian mechanics to estimate how far an ice-hockey puck could travel on a low-friction icy surface.

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Physics in the pandemic: ‘Watching a phenomenon of staggering scope unfold in real time, dictated by simple mathematics’ - Physics World

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I suspect my experience with the outbreak of COVID-19 here in British Columbia differs little from that of millions of others. My wife and I both work at the University of Victoria, and it was relatively easy for us to shift our teaching, research and collegial interactions online. The simulated and historical data that comprise the grist of my climate research are still accessible, so that work goes on unhindered. We are both lucky in that respect, and also to have shielded our family from the tragedy thus far.

In the days before being sent home from the office, I combed the Internet for reliable sources of data on the spread and growth rate of the infection: a nightly hobby only another scientist could appreciate. One conclusion was immediate: each country’s cumulative cases closely followed an exponential curve, with only China exhibiting a flattening and subsequent decline. I downloaded the daily case totals and performed log-linear fits to the data, revealing differing growth rates across the world. And in my province, checked daily for signs of flattening. While undeniably tragic, it’s also fascinating to see a phenomenon of such staggering scope unfold in real time, dictated by simple mathematics. When my 14-year-old son’s home schooling starts next week, you can guess what applied math topic we’ll tackle first.

Once the government imposed physical distancing guidelines, a neighbour asked my opinion (“as a scientist”), and shared his own. The government measures were certainly overkill, he felt: his clients were shuttering their businesses, this was killing the economy, why are they even talking about months? I agreed it was sudden, and uncharted territory. But the exponential curve danced in my head: these were not bacteria multiplying in a dish, but sick human beings, in every corner of the world. If there is anything that would kill the economy, I opined, it’s something that forces people out of it. We agreed to disagree.

And lessons learned so far? Here on Vancouver Island, at the end of the Trans-Canada Highway and near the end of supply lines to western Canada, we are occasionally reminded that we live in an earthquake zone. There’s a better-than-even chance a megathrust quake will occur in the region during my kids’ lifetime, we’re told. The COVID-19 experience has already taught us that, even in a global crisis, people keep their heads, large populations adapt, and there is considerable resilience in the consumer supply chain. We can trust the advice proffered by government and scientists, provided it is evidence-based. And when we encounter those who may be more sceptical, as scientists we can share our perspectives on the natural laws that no amount of wishful thinking can supersede.

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Physicists doing stupid things - Physics World

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When Physics World learned that an Australian astrophysicist had tried to invent a device to keep people from touching their faces during the coronavirus pandemic, only to wind up in hospital with four neodymium magnets stuck up his nose, our first thought was, “Is it April Fool’s Day in Australia already?”

Our second thought, though, was, “Yeah, that sounds like something a physicist would do.”

We write a lot about physicists. We’re regularly amazed and humbled by the creativity and cleverness they show in the face of daunting scientific challenges. But we also know that physicists have a rare talent for making absolute arses of themselves – and we have a giant red folder full of stories to prove it.

So this year, in lieu of an April Fool (and to reassure the above-mentioned Aussie, Daniel Reardon, that getting magnets stuck up your nose during a pandemic is not, in fact, the dumbest thing a physicist has ever done – although it’s close), we present five additional astonishing displays of idiocy by otherwise highly intelligent people. All are drawn from the Physics World archives and compiled by our emergency otolaryngology correspondent Ken Heartley-Wright, who is currently self-isolating at his country home in Borsetshire. Enjoy!

That’s not (n)ice

Like Reardon, Muhammad “Moe” Qureshi made a fool of himself while attempting to aid the battle against a terrible illness. In the “ice bucket challenge” of 2014, celebrities, politicians and ordinary folk lined up to pour buckets of ice over their heads to raise money for research on motor neurone disease. The late physicist Stephen Hawking, who lived with the condition for more than 50 years, was among the participants.

But Qureshi, who was then a nanotechnologist at the University of Toronto in Canada, decided to go one better than Hawking et al. “Instead of using ice water, we’re going to be using liquid nitrogen,” he announced to the camera as a collaborator filmed his don’t-try-this-at-home stunt. “This is extremely dangerous and not safe, but we’re going to do it anyway.” A few seconds later, the video shows Qureshi pouring a substantial quantity of steaming liquid nitrogen over his head.

Unlike Reardon, Qureshi did not require hospital treatment. However, the footage of him dancing around yelling “Oh my gosh, that’s cold!” while frantically trying to remove the 77 K liquid from his hair, T-shirt and shorts should nevertheless give would-be imitators pause.

Stranded tardigrades

Tardigrade
(Courtesy: Shutterstock/Sebastian Kaulitzki/HelenField)

Scientists have long wondered whether life exists outside the Earth. In April 2019, an Israeli space mission may have answered that question by accidentally populating the Moon with tardigrades. These creatures, also known as water bears, can survive in some of Earth’s most extreme environments, and they were flown to the Moon aboard the Beresheet spacecraft. During the landing process, however, a malfunction caused the craft’s engines to shut down, and it crashed to the lunar surface.

Beresheet’s crew of 10,000 tardigrades were shipped to the Moon in a dehydrated state, with a dramatically reduced metabolism. Tardigrades are, however, known to endure incredibly harsh conditions – including the vacuum of space. If they survived the crash, a little water might be enough to resurrect them. It’s a long shot, of course: tardigrades have poor tolerance to solar UV radiation, and the Moon (like some supermarkets during the current pandemic) has a distinct shortage of liquid water or food. But now we’ll always be wondering.

Legal troubles, part 1

In medieval and ancient times, alchemists sought to turn base metal into gold. In the late 2000s, Iain Fielden, a physicist at Sheffield Hallam University in the UK, managed to do the opposite by turning a £60 speeding ticket into court costs exceeding £20,000.

The affair began in mid-2006, when a speed camera clocked Fielden’s wife Vikki driving around a curved street in Huddersfield at 36 mph in a 30 mph zone. Fielden, who was sitting in the passenger seat at the time, insisted she was driving at 31±3 mph. He chose to fight the ticket because, he claimed, the speed camera was situated on a curve and would only work correctly for vehicles travelling in a straight line.

So far, so reasonable. But Fielden’s efforts quickly took on the character of a crusade. After a magistrate’s court handed down the £60 fine in 2007, he, his wife and two witnesses set out in the dead of night to measure the curvature of the road using a tape measure, rope and a laser. The results showed that the radius of the road was about 600 m – half the minimum value permitted in the camera manufacturer’s guidelines.

Fielden duly challenged the magistrate court’s ruling on the basis that the police were not using the radar in line with the guidelines. But despite spending 1000 hours researching the case (and, at one point, impersonating a lawyer for the Crown Prosecution Service during a phone conversation with a witness) he lost his appeal at Bradford Crown Court – one reason being that the limit of 1200 m for the curvature was, it seems, arbitrary.

By this time, Fielden’s legal costs had reached £15,000 – an amount he said would lead to “bankruptcy, probably”. But he didn’t stop there. Instead, he pursued the matter to the High Court, where, in mid-2009, one of the judges described the suit as “doomed to fail”, dismissed it and denied Fielden a further chance to appeal. This result cost him a further £5000 in legal fees. At that point, Fielden vowed to take his case to the European Court of Human Rights. While Physics World can find no record of his having done so, the protracted battle doesn’t seem to have diminished his interest in the law: he is now part of an expert witness programme at Sheffield Hallam’s Materials and Engineering Research Institute.

Legal troubles, part 2

Fielden’s problems with the law pale in comparison with those of Paul Frampton. A British-born theorist, Frampton made a name for himself within the field of particle physics. By 2012 he was a respected but decidedly un-famous professor at the University of North Carolina in the US.

All that changed when, at the age of 71, Frampton travelled to Bolivia in hopes of meeting the Czech-born lingerie model Denise Milani, with whom he had supposedly been corresponding over the Internet. When he arrived, Milani was nowhere to be seen, but someone did turn up with a request that he carry “her” suitcase to Buenos Aires, Argentina. This he duly did – only for airport officials to find 2 kg of cocaine tucked into its lining.

Exactly how much Frampton knew about this is a vexed question. While he has always maintained his innocence, text messages sent from him to “Milani” (in reality, a fraudster whose identity remains unknown) suggest that he may have been less naïve than he claims. According to a 2013 New York Times article, the texts included comments such as “This stuff is worth nothing in Bolivia, but millions in Europe” and “Monday arrival changed. You must not tell the coca-goons.”

At his trial, Frampton claimed the messages were “jokes”; later, he hired a forensic linguist to try to prove he hadn’t written them. Neither strategy did him much good. He was sentenced to 56 months in a Buenos Aires jail, and his former employer refused to reinstate him. Still, his experiences may yet have a silver lining of sorts. In 2013, Fox Searchlight asked officials from the US film-production company Film Rites to make a film based on his life. We can only assume that the pandemic must have held up production.

Acid attack

And finally, in our roll-call of dumbest things ever in physics, Physics World is delighted to bring you this cautionary tale of Irish physicist Kevin McGuigan during his time as a PhD student.

Seeking to dope some silicon ingots with copper, McGuigan decided to melt a glass tube containing his ingredients by heating them in a furnace at 1000 °C using an “oxygen-hydrogen welding station” in the corner of his lab. Upon opening the main valves to the gas cylinders, McGuigan noticed an ominous hissing noise that he wanted to “sort out” with a “small twist” of his spanner.

Physics World October 2002
Cack-handed: a warning to all would-be Kevin McGuigans

Aware that hydrogen is dangerously flammable, McGuigan “panicked” and began turning the fittings on the cylinder “the wrong way”. The regulator refused to budge, prompting McGuigan to increase his “purchase” on the bottle, by wrapping his legs around the base “in an attempt to stop it spinning”.

Then, just as McGuigan was having visions of a Hindenburg-style disaster, his supervisor walked in. Upon seeing him wrapped around the hydrogen cylinder “wrestling with the regulator like a demented, pole-dancing plumber”, his boss calmly closed the cylinder’s main valve.

A nightmare was averted, but McGuigan’s day was about to take a turn for the worse.

After doping his samples, McGuigan placed them in a beaker of concentrated hydrochloric acid. While attempting to dissolve “the final traces of copper from the ingots”, he held the beaker up to the light “as you would with a fine wine”. Finally, he tried to inspect the samples’ surfaces by giving the beaker, as you do, “a good slosh”.

As luck would have it, the acid sloshed right out of the beaker and onto his groin. McGuigan jumped up, unbuckled his belt and trousers, and thrust them down by his ankles. Noticing the acid making its way onto his boxer shorts, he yanked them down too before “speed-shuffling over to a metal sink” and vigorously dousing his nether regions in water.

It was then that McGuigan’s supervisor, the head of department and a visiting female professor walked in – on an impromptu tour of the lab.

Although McGuigan was unscathed “apart from what looked like a pubic perm gone wrong”, his supervisor and the department head agreed that henceforth, McGuigan’s “theoretical and modelling skills should be enthusiastically encouraged”.

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Tips for a rewarding career in physics - Physics World

Most of the time science appears in the media – including in this podcast – the focus is on the scientific results. Rightly so, as scientific research consistently delivers inspiring breakthroughs. But this type of coverage can present an idealized version of science. Researchers are presented as dispassionate beings working together seamlessly to uncover the common truths of their discipline.

In reality, scientists are people with a range of personalities and backgrounds, displaying all the usual human traits – the good and the bad. In this episode of the Physics World Stories podcast, Andrew Glester meets a selection of successful researchers to discover what it is really like to carve out a career in physics. What motivates them? What are the big challenges lying ahead for early-career researchers? What are the rules they play by?

For more information and advice on this topic, see the 2020 edition of Physics World Careers. In the March issue of Physics World magazine, we also launched our new “Ask me anything” interview series, providing careers advice for physics graduates. Physics World’s Tushna Commissariat asks 10 of today’s top physicists three questions to find out about their roles and what they wish they knew when they started their careers.

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Solar wind and extreme heat creates ice on Mercury, say researchers - Physics World

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Some of the ice on Mercury is created by chemical reactions triggered by the planet’s extreme daytime heat according to Brant Jones and Thomas Orlando at the Georgia Institute of Technology and NASA’s Menelaos Sarantos.  The trio discovered the process by modelling the chemistry that unfolds as the solar wind impacts the planet’s surface. Their discovery could explain the presence of up to 10% of Mercury’s total water ice, and also provide new insights into how water could be created on the Moon.

Despite its daytime temperatures reaching as high as 400 °C, Mercury is known to host vast quantities of frozen water in the deep, permanently shadowed craters close to its poles. First discovered by Earth-based radar systems, this ice has now been precisely mapped by NASA’s MESSENGER spacecraft, which has been in orbit around Mercury since 2011. Astronomers believe that most of this water was delivered by impacting asteroids and comets. They also think the ice has remained trapped for millions of years in shady areas where temperatures remain permanently below -200 °C.

In this latest study, Jones, Orlando and Sarantos describe how protons in the solar wind may also be creating water on the planet. The trio developed a model that suggests that the protons can penetrate to depths of up to 15 nm into Mercury’s surface soil. There, the protons react with metal oxides to form hydroxyl (OH) groups. In Mercury’s extreme daytime heat, these groups can react with each other to form gaseous water, along with molecular hydrogen.

Exospheric journey

The trio then simulated how water behaves in Mercury’s exosphere – the planet retains no atmosphere but is surrounded by an exosphere of atoms and molecules kicked up from the surface. Water in the exosphere is transported across the planet through a variety of mechanisms. Some of these molecules rise far above the surface, while others are split into fragments.

However, the simulation revealed that some water does become trapped in the chilly polar craters, which occupy around 1% of Mercury’s total surface area. The trio predict that this process could account for around 10% of Mercury’s frozen water.

The result could shed new light on the differences between the ice-forming mechanisms found on Mercury, and those of other airless bodies like the Moon. The Moon has far cooler temperatures than Mercury, so the solar wind is far less likely to produce hydroxyl groups. This would explain why water ice does not appear to be nearly as abundant in the Moon’s craters as in Mercury’s. Instead, the trio hopes that their findings could lead to the development of new techniques for fabricating water on the Moon – which could be crucial for future space missions.

The research is described in The Astrophysical Journal Letters.

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Diamond defects could boost the range of quantum cryptography - Physics World

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A new type of quantum memory that could extend the range of quantum encryption systems has been unveiled by physicists at Harvard University in the US. It offers a secure way of allowing an intermediate to assist in the transmission of quantum information and could lead to the more widespread use of quantum key distribution (QKD) cryptography.

Using QKD, two people (Alice and Bob) rely on quantum mechanics to exchange information secretly. Alice sends Bob a series of quantum bits (qubits) encoded into the polarization states of single photons (or weak coherent light pulses). By carrying out a series of measurements and communications over an insecure link, Alice and Bob generate an encryption key that they can use to send secret messages over an insecure link. Crucially, if an eavesdropper (Eve) intercepts and measures the quantum bits, Alice and Bob are alerted thanks to the laws of quantum mechanics.

Although some commercial QKD systems are in use, sending single-photon qubits over long distances in optical fibres is a significant technical challenge. The current record for QKD over a commercial telecom link (rather than a dedicated link) is 50 km.

“Photons get lost”

“At its core, the reason we don’t have a quantum internet right now is that photons get lost,” explains team member Bart Machielse: “Photons are scattered out of fibres, photons are absorbed, and as the links get longer the communication rate goes down.” Incorporating multiple photons into each pulse would remove the absolute security, as Eve could measure one photon without disturbing the others.

One possibility is to incorporate a third party (Charlie) between Alice and Bob to measure the states of the photons they exchange. However, if the security is to remain absolute, Charlie cannot simply measure the state of a photon from one party and compare it to the next photon he receives from the other, as he may not be trustworthy himself.

Here, too, quantum mechanics offers a solution: Charlie compares the polarizations without knowing their individual values.  “Charlie does measurements on both photons and says ‘These are the same’ or ‘These are different’,” explains Machielse, “Alice and Bob say ‘I know what photon I sent’ and ‘Charlie tells me our photons are the same or different’.” This preserves the security of the communication even over an insecure link.

Simultaneous measurements

One problem with current technologies is that to make a secure comparison, Charlie must receive the photons simultaneously from Alice and Bob – which happens rarely. Researchers have therefore tried to develop a quantum memory that allows Charlie to store the quantum state of a photon he receives without measuring it. “People have used memories ranging from trapped atoms and ions, quantum dots, different defects in diamonds, you name it,” says Machielse. None of these, however, have actually improved over what can be achieved by direct photon exchange.

In the new research, Machielse and colleagues created a memory using a silicon vacancy centre (Si-V) in a diamond. A Si-V is a defect formed when two carbon atoms in the diamond lattice are replaced by one silicon atom. This creates a quantum spin that is isolated from the environment and can be measured using laser light and microwave pulses.

The team placed their Si-V inside a nanophotonic cavity held at ultracold temperatures. The spin of the Si-V can be flipped by absorbing a 737 nm wavelength photon. If the spin state of the Si-V does not change after absorbing two photons, Charlie knows that the two photons had the same polarization as each other. If the state has been flipped, the polarizations must have been opposite. Crucially, however, Charlie does not know the polarization of either photon.

Another key feature of this implementation is that the photons from Alice and Bob do not have to arrive simultaneously at the Si-V. Instead, the Si-V stores the polarization of the first photon until the arrival of the second.

The Si-V-based quantum memory achieves both very strong and very reliable spin-photon interaction. “With a lot of the other memories, either not every photon that arrives is stored, or an error happens in the storage process and the information is essentially useless,” explains team member Ralf Riedinger, “We achieved low enough error rates that, even after correcting for the errors, we still achieved faster communication than anything possible with a direct communication link.”

The researchers describe their work in Nature. Sophia Economou of Virginia Tech in the US says “This is a very significant paper: I would call it a milestone in the field of quantum networks”. She believes the work opens up “several future directions” such as transferring information from the electronic spins of the Si-V centres to the more stable nuclear spins of the surrounding carbon-13 isotopes in the diamond: “Achieving this would allow storage of information for longer periods of time, boosting performance of the protocol and opening more opportunities for quantum networks,” she says.

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Carbon nanotubes forecast when vegetables spoil and buds bloom - Physics World

When one bad apple rots the bunch, it’s ethylene’s fault. Not only does this “universal plant hormone” trigger germination, flowering, ripening and rotting in seeds, flowers, fruit and vegetables, it’s also released during these processes, ensuring that a small problem quickly escalates. Ethylene is social media for plants, allowing them to communicate and synchronize – and it’s something the food and flowers industries would love to detect early, so they can forecast which products to sell first, and how to spot rot before it spreads.

The problem? “There really isn’t a good industrial sensor out there,” says Timothy Swager, a materials chemist at the Massachusetts Institute of Technology (MIT) in the US. Now, however, Swager, Darryl Fong and colleagues at MIT and the Nanotechnology National Laboratory for Agriculture in Brazil have combined the sensitivity of carbon nanotubes (CNTs) with a highly selective catalyst to produce a sensor that can detect ethylene at concentrations of as little as 15 parts per billion.

CNT sensing

Previous approaches to ethylene sensing have typically either been based on photoacoustic spectroscopy (which detects sounds produced in response to light) or on gas chromatography (which separates chemicals based on their different retention times in solvents). Neither technique is easy or simple enough for a grocer or florist to incorporate it into their work. Instead, Swager and colleagues looked at the reactions ethylene readily undergoes and focused on finding ways of detecting when such a reaction had taken place.

This is where the CNTs come in. Single-walled CNTs have several attributes that make them well-suited for sensing processes that involve the transfer of electrons – the basis of any chemical reaction. The CNTs Fong and Swager and their colleagues worked with are p-type semiconductors, so n-type dopants – anything that donates electrons to the CNT – will diminish their conductivity. The CNTs’ curved graphene surface also makes their electronic properties incredibly sensitive to dopants in their environment.

This may sound ideal for a sensor, but you can have too much of a good thing. “There’s a graveyard of CNT sensors with low specificity,” Swager tells Physics World. Because the CNTs are so sensitive to everything in the environment, he explains, all you detect is white noise. “You need a way of boosting the signal above the noise,” he adds.

Wacker reaction chemistry

Building on their expertise in analytic and synthetic chemistry as well as CNT technology, Swager and colleagues identified the so-called Wacker reaction as having both the specificity and sensitivity they needed. In this reaction, which was developed as a synthetic process in the 1950s, ethylene – a hydrocarbon containing two double-bonded carbon atoms – oxidizes into acetaldehyde. This chemical is perhaps best known as the primary cause of hangover-related headaches, although the researchers note that the test they developed does not produce it in high concentrations.

The Wacker reaction is not the only reaction ethylene undergoes, and it was not the first port of call for Swager and his group. First, they tried to mimic the plants themselves, which use copper ions to promote ethylene activity. However, trying to make a sensor out of copper proved almost as headache-inducing as acetaldehyde. Plants have a natural ability to keep copper in its Cu(I) oxidation state, which has one fewer electron than the material would have as a neutral atom. Ethylene readily binds to copper in this oxidation state, triggering a cascade of plant activity and ultimately the up-regulation of certain genes. However, in a synthetic device, copper tends to exist in the Cu(II) oxidation state, and preventing Cu(I) from oxidizing to Cu(II) proved too difficult for this approach to have commercial potential.

In the Wacker reaction, in contrast, ethylene oxidation is catalysed by palladium in the Pd(II) state. This is far more stable than Cu(I). Although palladium can catalyse other reactions as well, the palladium in the Wacker reaction is in an organic complex optimized to catalyse ethylene oxidation. The reaction also relies on a nitrite source, which contributes to the organic complex. The resulting ethylene reaction surrenders electrons that reduce Pd(II) to the n-dopant Pd(0), which the highly sensitive CNTs should announce with a dip in conductivity from the excess electrons.

Budding commercial potential

The researchers tested their proposed mechanism by replacing the CNTs with ZnO nanofibers, which are n-type semiconductors. This test showed that, as expected, the material’s conductivity increased in response to the Pd(0) produced in the presence of ethylene and the Wacker reaction Pd(II) catalyst. Next, they optimized their CNT-based sensor and used it to detect ethylene production from carnations (which, in their experiment, all burst into bloom on the same day) and purple lisianthus (which bloomed over the course of a week). They found that the ethylene they detected reflected these different blooming times.

The process is now licensed by a company that Swager co-founded, but some hurdles remain before the sensor is available commercially. “We could industrialize these sensors in a matter of months, but how long before it is commercialized is something the business world will control,” Swager says.

The researchers describe their work in ACS Central Science.

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Physics in the pandemic: ‘Scientists don’t live in a vacuum’ - Physics World

The shutting down of my department was a surprisingly difficult day. The Imperial College chemistry department made the decision to shut on 16 March, when the first social distancing measures in the UK were announced, and I was not prepared for the emotional toll it would take on me. I’m in the last year of my PhD and was preparing to focus on a difficult year of work. Instead, I found myself putting away all my experiments and taping shut our freezers.

We’d all talking about it; we even had an informal bet on when the college would finally shut. Everyone had been on edge for a couple of weeks, and no-one could talk of anything else. I’m grateful that we shut down in the end though. Social distancing in London is very difficult and, as anyone who has been on the tube will know, sometimes it’s just impossible.

So now I’m at home writing my thesis. I have my desk set up by my window and a routine established. At least that’s what I’m supposed to be doing. My brain hasn’t quite worked out a way to stop worrying enough to work properly. I’m trying to be kind to myself; scientists don’t live in a vacuum and the state of the world will affect our work. Trying to adjust to the massive changes we’ve all experienced in the past month is no small task.

As an experimental scientist, all my work is lab based. Like many around the world, I’m faced with the uncertainty of not knowing when I’ll be able to get my next results. I have an ever-expanding list of experiments that I want to do when I can return to the lab. In the meantime, like many other scientists, I’m going to try to learn all these computational and programming techniques that have been passing me by for years. Prepare for some very mediocre modelling!

Whilst I was trying to settle into the new rhythm, one of my flatmates developed symptoms. Which means that now we’re self-isolating as well. This has added an extra layer of worry, as I’m constantly concerned about her health and waiting to see if I get it. Hearing her coughing from my room, I’m continuously reminded how serious this crisis is.

One of the positives I’ve managed to find though, is that my research group has banded together. Everyone has been checking in on each other and putting online coffee sessions and Friday drinks in the calendar. We had our first virtual group meeting and I was struck by how much it started to make me feel normal again. Through all of this I’ve been overwhelmed by the amount that people are reaching out and making connections. It’s these interactions that are becoming my inspiration, lifting my spirits enough to be able to put pen to paper.

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Phase-contrast imaging could improve breast cancer diagnosis - Physics World

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Propagation-based phase-contrast CT (PB-CT) is an advanced X-ray imaging technology that can generate higher quality diagnostic breast images than absorption-based CT (AB-CT), at a glandular radiation dose comparable to, or lower than, conventional mammography and digital breast tomosynthesis (DBT). The technology is currently limited to use with synchrotron light sources, but the evolution of compact light sources may make clinical application feasible, improving the detection and diagnosis of breast cancer.

A multidisciplinary collaboration – including scientists from the University of Sydney, University of Melbourne, Monash Health, Maroondah Breastscreen and the Australian national science research agency CSIRO – is working on the clinical application of PB-CT using the Imaging and Medical Beamline at the Australian Synchrotron. The researchers have now optimized the technique using 12 mastectomy samples that included different tumour types or benign lesions. They showed that PB-CT achieved significantly higher image quality than AB-CT and demonstrated that substantially lower doses could be used with PB-CT (Acad. Radiol. 10.1016/j.acra.2020.01.009).

Phase-contrast imaging, which exploits both the refraction and the absorption of transmitted X-rays, offers potential to overcome the limitations of current breast imaging modalities. The 3D images produced by DBT reduce the tissue superimposition effects of 2D mammography, but have lower sensitivity in detection of calcifications. Breast MRI has higher sensitivity than mammography, but lower specificity. It is also a highly expensive examination. Breast CT, meanwhile, visualizes mass lesions better than mammography, but underperforms with respect to depiction of microcalcifications and has poorer spatial resolution. In addition, its radiation dose is the highest of the breast imaging modalities.

PB-CT, one technique for phase-contrast imaging, is based on free-space propagation and the use of phase-retrieval algorithms to fully use the refraction information. The PB-CT method measures the phase shift as intensity modulation at the detector by simply positioning the detector a few metres from the object. Unlike other phase-contrast imaging techniques, it does not require any special X-ray optical elements in order to render the X-ray refraction visible. The only key requirements for PB-CT are a long propagation distance between the object and the X-ray detector, and the use of highly spatially coherent incident X-rays, produced by synchrotrons or compact X-ray sources.

The group previously demonstrated that PB-CT could reconstruct images with high quality and high diagnostic value, with a dose comparable to that of 2D mammography. In this latest study, led by Patrick Brennan, the team employed 32 or 34 keV X-ray beams from the synchrotron to scan the mastectomy specimens using PB-CT and AB-CT techniques under varying conditions.

The researchers collected images at two sample-to-detector distances: 0.19 m to represent an AB-CT scan and 6 m for a PB-CT scan. All AB-CT images were collected at a “standard” mean glandular dose of 4 mGy, using 2400 projections with 0.075° angular steps. PB-CT images were collected at both 4 mGy (2400 projections with 0.075° angular steps) and 2 mGy (1200 projections with 0.15° angular steps). The team used an ionization chamber to measure the photon fluence rate and the corresponding rate of the surface absorbed dose to air at the ionization chamber plane.

AB-CT vs PB-CT
Absorption-based CT (left) and propagation-based phase-contrast CT (right) of a breast mastectomy sample, both using a dose of 4 mGy. (Courtesy: Seyedamir Tavakoli Taba)

After three radiologists selected the best quality AB-CT image set for each mastectomy specimen, 11 radiologists independently compared the overall image quality in PB-CT images, prepared in axial and sagittal planes, with the corresponding AB-CT images. They evaluated lesion sharpness, visibility of calcifications, image noise, perceptible contrast, visible artefacts and normal tissue interfaces.

The radiologists reported that PB-CT images acquired at both standard and low dose were of significantly higher image quality than the AB-CT images. The researchers also determined that PB-CT images obtained at 32 keV and reconstructed using half phase retrieval (rather than full phase retrieval) had the best overall image quality.

First author Seyedamir Tavakoli Taba tells Physics World that the team will soon start a receiver operating characteristic (ROC) study to compare the diagnostic efficacy of PB-CT with conventional breast imaging techniques, such as mammography and DBT. To date, the researchers have scanned over 75 fresh breast mastectomy samples and anticipate scanning another 50 before launching the first clinical trial, planned for early 2021.

“Our plan is to establish a world-first mammographic PB-CT clinic at the Australian Synchrotron in three to four years, to be used mainly for staging and treatment options,” says Taba. “The widespread clinical implementation of PB-CT can be delivered via commercially available compact X-ray sources in the future. This will allow PB-CT to be widely translated into specialist cancer care facilities across Australia and overseas.”

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Condensed-matter physics pioneer Philip Anderson dies aged 96 - Physics World

The US condensed-matter physicist Philip Warren Anderson died yesterday aged 96. One of the most celebrated condensed-matter physicists of his generation, Anderson’s theoretical research into the electronic structure of magnetic and disordered systems led to an improved understanding of metals and insulators. For this work he was awarded the Nobel Prize for Physics in 1977, which he shared with the British physicist Sir Nevill Mott and the US physicist John Hasbrouck van Vleck.

Born on 12 December 1923 in Indianapolis, Indiana, Anderson was raised in Illinois, where his father taught plant pathology at the University of Illinois in Urbana. In 1940, Anderson went to study physics at Harvard University but during the Second World War was drafted to work at the US Naval Research Laboratory, spending the period from 1943 to 1945 researching antenna design. He then returned to Harvard working on a PhD under the supervision of  van Vleck, graduating in 1949.

Anderson then joined Bell Telephone Laboratories in New Jersey, which was part of the telecoms firm AT&T. It was there that he developed his theory of the electronic structure of solids.

Much of what we know about the electronic properties of metals and semiconductors is based on the idea that electrons with certain momenta can travel freely through a crystalline lattice, while others cannot. This is embodied in Felix Bloch’s 1928 quantum theory of conduction, which describes the lattice as a periodic electric potential through which some electrons (behaving as “matter waves”) diffract with ease. In the 1960s, Anderson worked out what would happen in such a system if the potential lost its periodicity. This could happen, for example, if the lattice remained periodic, but the potential has a different value at each lattice site.

Anderson found that electrons would be unable to move through such a “disordered” lattice, and instead become trapped by specific atoms. If the disorder is sufficiently strong, the electrons cannot form an electric current due to destructive interference between different scattering paths. Instead, they become localized and unable to propagate in space.

For this prediction of what became known as “Anderson localization” he was awarded the 1977 Nobel Prize for Physics, which he shared with van Vleck and Mott for their “fundamental theoretical investigations of the electronic structure of magnetic and disordered systems”. Anderson localization has since been seen in several systems including those based on light, microwaves and in atoms held in a Bose–Einstein condensate.

A ‘wonderful’ lab

The 1960s was a particularly productive time for Anderson. He also worked on the theory of superconductivity, in which the electrons in a material can flow without resistance, and explored the properties of helium-3. In 1967, Anderson spent eight years on a part-time basis at the University of Cambridge before returning to the US to work at Princeton in 1975, while still being affiliated to Bell Labs.

Anderson retired from Bell Labs in 1984 when the US government disbanded AT&T and began working full-time at Princeton where he continued his research on spin glasses – nonmagnetic metals embedded with randomly spaced magnetic elements – as well as high-temperature superconductors.

In an interview with Physics World in 2006, Anderson said that he mostly enjoyed his 35 years at Bell Labs. “For the first three decades it was the most wonderful laboratory in the world,” he said. “We had freedom, an enlightened management and a personnel department that never had any say in the direction of the research department. We had a very high opinion of ourselves, but it was justified. Those were the years when we invented modern technology.”

The ‘arrogance’ of particle physics

Anderson also made crucial contributions to other fields in physics. In particular, in 1962, he published a now-famous paper on how the photon acquires mass. It was cited two years later by Peter Higgs in his own paper on the discovery of a mechanism for understanding the origin of mass – a theory for which Higgs and François Englert won the 2013 Nobel Prize for Physics. The mechanism was later confirmed by the discovery of the Higgs boson at CERN’s Large Hadron Collider in 2012.

While Anderson had noted that the Higgs boson could have been called the “Anderson–Higgs boson” in recognition of his work, in 2013 he told Physics World that the Swedish Academy made “a perfectly reasonable decision” to award the prize to Higgs and Englert. “I also think the fuss over the theoretical part of the work a bit excessive relative to the gigantic experimental effort,” he added.

In the late 1980s, Anderson was a vocal critic of the $4.4bn Superconducting Super Collider (SSC), which the US was planning to build in Waxahachie, Texas, as the next big machine in particle physics. In 1987, Anderson famously gave testimony to the US Senate, in which he worried that the huge costs of the 87.1 km circumference circular collider would force cuts to other science budgets. He was far from the only physicist who had such concerns and, despite some $2bn eventually being spent on digging parts of the SSC’s underground tunnel and constructing various buildings, the collider was cancelled in 1993, by which time the project’s estimated final price tag had almost trebled to $12bn.

Indeed, Anderson held a sceptical view of particle physics and the belief in the field by some that it deserved more funding that other areas. “There is a great arrogance and immodesty about that whole field, which gets on my nerves,” he told Physics World in 2006. “Particle theorists say [they’re] discovering ‘the mind of God’. It’s not the mind of God at all. In the first place, there’s no God, and in the second place, particle physics cannot explain things like superconductivity, life and consciousness. It makes no contribution to explaining how the world actually works.” He also held the view that particle theorists owe more than they realize to condensed-matter theorists like himself, particularly for having developed the concept of “broken symmetry” in the 1950s.

Emergent views

During his career, Anderson wrote several scientific books, including Concepts of Solids, Basic Notions of Condensed Matter Physics (1997) and More and Different (2012). He also contributed to the philosophy of science, writing a now famous article “More is Different” for Science in 1972. This set out the limitations of “reductionism”, according to which all of science can, in theory, be derived from just a few fundamental principles.

Anderson instead believed in “emergence”, which states that everything we observe at one level obeys the laws at a more primitive level, but that those observations cannot necessarily be deduced from that level. He even dubbed it the “God principle” but told Physics World that it did not reflect any religious beliefs. “I’m not quite as atheistic as [Oxford biologist] Richard Dawkins, but I’m very close,” he said.

Anderson received the National Medal of Science in 1982 and was involved with the formation of the interdisciplinary Santa Fe Institute, which explores the science of complexity. He joined as an emeritus professor in 1985 and in 1996 Anderson became an emeritus professor at Princeton.

Indeed, Anderson remained active as a physicist well into his 80s and 90s, even being named as the “world’s most creative physicist” by one statistical analysis in 2006. He continued to review books, including a review for Physics World in 2013 of a biography of his near-contemporary Freeman Dyson, who died in February. His last letter to Physics World was published in 2017.

Outside physics, Anderson was a keen hiker and gardener as well as an enthusiast of the Chinese board game Go where he was a certified “first-degree master”.

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Physics in the pandemic: ‘I learned that my students miss the structure and support that the university provides’ - Physics World

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It’s been two weeks since Trent University shut down. We all knew it was coming, but its abruptness came as a real shock. On Thursday night, I was making final preparations for Friday lectures (one of my heavy teaching days), and on Friday morning everything was closed. Now, the term is winding down and we’re all trying to figure out how to move exams online.

Despite the upheaval, it’s easy to feel removed from everything that’s going on in the wider world. Peterborough is a small city two hours north-east of Toronto, plunked in the middle of lakes, cottages and farmland. Birds have been streaming back into the area now that winter has ended, and the seasonal renewal contrasts strangely with the constant messaging around the virus. Social distancing is almost effortless here: I can easily wander the streets around my neighbourhood without crossing paths with another person, and a 10-minute drive takes me out onto quiet railway trails through the countryside.

In many ways, my life has become simpler since the shutdown. I still have lots of work to do, but the interruptions have disappeared. As I have recently learned, this is not necessarily true for my students. Indeed, the strangest aspect of the shutdown has been losing touch with them. Trent is a small university, with a lot of interaction between students and faculty, and I hadn’t realized how much student feedback informs my teaching.

Twelve time zones away

To fill the void, I posted a survey with one question (“How are you doing?”) and discovered that they were eager to share. Most have left town, and are back in their parents’ houses, including the international students who are now up to 12 timezones away. For some, the return home comes with emotional stress that makes it hard to focus on coursework; others are grateful for the extra support that their families provide; and more than a few confessed that they have been “on vacation” since the shutdown.

More seriously, a few students are anxious because they have family members with serious health problems that make them susceptible to the virus. Ultimately, I learned that my students miss the structure and support that the university provides. But they adapt: some continue to study together using Discord, a Skype-like app specifically designed for gamers, while others build new daily routines. I hope they are ready for the real challenge that comes next week: exams.

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Black hole ‘subrings’ could be seen by putting a telescope on the Moon - Physics World

Adding a space telescope to the earthbound Event Horizon Telescope (EHT) should reveal the delicate series of light rings surrounding a supermassive black hole – according to a team of astrophysicists in the US. As well as providing more precise values for the mass and spin of a black hole, observing these “subrings” could also be a benchmark test of long-baseline interferometry using telescopes on Earth and in space.

In April 2019, scientists working on the EHT observed a glowing ring of light surrounding the supermassive black hole that lies at the heart of the M 87 galaxy. This first observation allowed the EHT team to determine the mass of the black hole to 6.5 billion solar masses, give or take 10%. EHT scientists we also able to work-out the direction of rotation (spin) of the black hole.

This light comes from hot matter swirling around the black hole. The light is deflected by the black hole’s immense gravitational field, making it appear like a ring to a distant observer. However, what the EHT was not able to discern is a series of subrings within this ring that should provide important information about the black hole.

A glimpse of complexity

“With the current EHT image, we’ve caught just a glimpse of the full complexity that should emerge in the image of any black hole,” says Michael Johnson of Harvard University, who was involved in this latest research.

Each of these subrings corresponds to a specific set of trajectories taken by the deflected light. Most of the light in the ring is the result of small deflections, which create a diffuse halo-like subring that is denoted n=0. Light can also follow a parabola-like path, doing a half-orbit of the black hole before escaping. This light is focussed into a thinner ring within the halo denoted n=1 because the light has made one half-orbit of the black hole.

Some light will complete one orbit of the black hole before escaping to create the even thinner n=2 subring. Indeed, a series of increasingly thinner rings are created by light that completes increasingly higher numbers of half-orbits of the black hole. As the number of half-orbits increases, the subrings also shrink in diameter and become less bright.

Very, very large arrays

Now, Johnson and colleagues have calculated the structure of these subrings and concluded that it should be possible to observe them using telescopes that are separated by very large distances.

The EHT is a network of radio telescopes that span a hemisphere of the Earth. Using a technique called very-long-baseline interferometry, the EHT is effectively an Earth-sized radio dish, which gives it extremely high angular resolution. In this latest work, the researchers have calculated that even this huge telescope is not good enough to discriminate between the first few subrings.

One way of spotting the n=1 subring, they say, could be to use a ground-based array of telescopes that are sensitive to lower-wavelength signals than the EHT. Another, possibility would be to launch radio telescopes into low-earth orbit. Detecting the n=2 ring would require a telescope on the Moon and seeing n=3 would require a telescope at the L2 Lagrangian point beyond the Moon.

The team says that one future option would be to use the Russian Millimetron mission which is expected to launch to L2 in 2029.

The research is described in Science Advances.

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How physics is helping in the war against COVID-19 - Physics World

The COVID-19 pandemic has led to a state of global emergency. In such an interconnected world, the virus is spreading fast and cares little about national borders. Fortunately, scientific knowledge and public health responses are more advanced now than ever before.

Medical doctors, nurses and other medical staff are on the frontline of dealing with the consequences of the pandemic. Behind them, scientists from a range of fields are working intensely to better understand the virus behind the pandemic: SARS-CoV-2.

How exactly does it infect humans then spread between us? Who is most at risk? Can we develop a vaccine and drugs to defend ourselves? Where should we focus our resources? These are just some of the many difficult questions faced right now by healthcare professionals, research scientists and politicians.

This short video looks at how physics and physics-based technologies can play a role in tackling these questions. To find out more about how physics is helping in the global response to COVID-19 see this article by science writer Jon Cartwright.

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Physics in the pandemic: ‘I’m worried about paying for medical treatment’ - Physics World

Haley Harrison in front of her computer
Nanoscience PhD student Haley Harrison is catching up on writing, analysis and quality time with her five-year-old daughter – not necessarily in that order. (Courtesy: Haley Harrison)

I am a third-year doctoral candidate in nanoscience at the University of North Carolina, Greensboro, US, and my research focuses primarily on nanoscale surface modification. On most of my workdays, I’m in a typical wet chemistry lab or doing spectroscopy, but I also spend one week every month at NASA’s Glenn Research Center in Cleveland, Ohio.

Two weeks ago, when everything began shutting down and the US Center for Disease Control was increasingly urging people to travel home and stay there, I was doing work at Glenn Research Center and my five-year-old daughter was with my sister, who graciously watches her when I travel. When I got back, I briefly went to my university campus to finish up some last-minute experiments, although this was discouraged. Things happened fast, and my university has been diligent about shutting things down, but the labs are still open with some restrictions in place – for example, using gloves to open doors and only having one person in a lab at a time. They have also cancelled all instrument training, and technicians are operating most instruments for now.

Since then, my PhD adviser has pretty much ordered us not to work in the lab, so I won’t be back until May. I am currently working remotely and communicating with colleagues via e-mail and in shared Word documents. I know my project trajectory will be significantly altered if I can’t be in the lab this semester, which is hard to accept. I am sad that my research isn’t going to go as planned, but with the health of the world at stake it is a small price to pay.

Family concerns

On the personal side, my mom and I live together, and she just finished her cancer treatment. Normally, this is a momentous occasion, but due to the restrictions at hospitals she went to her last treatment alone and we didn’t get to see her ring the “I beat cancer” bell. She then drove directly to work. It is stressful knowing she is putting herself at risk, but her job isn’t guaranteed if she doesn’t go in. My daughter and I are taking extra precautions because Mom’s immune system is compromised from her cancer treatment, which means she is at a higher risk of complications from COVID-19. We send one family member to get groceries once a week and rely on various delivery services in the meantime.

My sister has been unofficially “furloughed”, which means she is on unpaid leave from her job. And she works for the state government! Don’t even get me started on how embarrassing it is that they would put her on unpaid leave. Although some employers are being proactive, others are clearly showing their complacency and leaving their employees to fend for themselves at this uncertain time.

As for me, I have a kindergartener at home and my priority will always be to make sure her needs are met. That means I’m at the mercy of the school system: as long as her school is closed, I’ll be at home, and caring for and educating a kindergartener doesn’t leave much time for doing anything that isn’t kindergarten.

Facing uncertainty

Apart from that, my biggest concern is the uncertainty. I am a graduate student, and our health insurance and pay is never guaranteed outside of our nine-month contracts. I am worried about paying for medical treatments if I do get sick, or if someone else in my family gets sick. I am worried about what will happen for us financially if social distancing goes into the late spring and early summer, as summer funding is always precarious even in a normal year and taking internships/childcare may not be an option.

There are some silver linings for me, though, at least temporarily. Because I have a bad habit of filling my lab notebooks with ideas and collecting lots of data all at once, I have lots of writing and analysis to catch up on. I find this one of the hardest parts of being a PhD student, so I could really benefit from taking this time to go through my work slowly and dig out mistakes so I can meticulously strengthen the skills I feel are weakest. Also, at my university, we have an open office setting, so it is nice to be able to think without having a colleague walking past every few minutes asking what I’m up to.

A final benefit is that I love spending unstructured time at home with my daughter. I’ve been a graduate student for most of her life, so I haven’t had this kind of time at home with her since she was very little. I suffer from “mom guilt” as a result – putting her into daycare was hard. Now I love sitting and listening to her tell me about all the things that go on in her little mind. We have been making the most of this time by playing, drawing, watching movies and catching up on endless craft videos on YouTube.

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