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If conferences did post-talk analysis interviews, space lettuce is on the menu, dimming Betelgeuse may just be dust

Some readers may be secretly pleased that conference cancellations have spared them the arduous task of presenting their results at a scientific meeting. Many of us have finished talks feeling like we’ve spent a few rounds in a boxing ring or a period or two on a hockey rink. So why not do a post-talk analysis interview like a professional athlete? This very funny video (below) by the Irish medical researcher Ciaran Fairman shows how it could be done– including how to gracefully critique the unfortunate colour scheme of a senior colleague’s slides.

Ever wondered what it would be like if academics gave post-match conferences?

Twitter's been heavy the past few weeks, figured I'd try brighten it up a bit!

Look after those university credit cards folks. pic.twitter.com/GyqICzOIUb

— Ciaran Fairman, PhD (@CiaranFairman) March 8, 2020

Lettuce is something we take for granted here on Earth. Lots of different varieties can be found in a supermarket and the leaves can be easily grown in the garden – as long as the slugs can be kept at bay.

But in space, fresh lettuce would be a much-appreciated addition to the usual packaged fare and the leaves also contain more vitamins than prepared foods.

Now, a team led by NASA’s Christina Khodadad has done a study of red romaine lettuce grown on the International Space Station. They found that the space lettuce is free of disease-causing microbes and is as nutritious as plants grown on Earth.

Safety and nutrition had been concerns because the crop was grown in lower gravity and more intense radiation than found on Earth. However, astronauts did nibble on some leaves before they were tested – suggesting that they weren’t particularly concerned.

Future tests will look at other leafy crops as well as small fruits like peppers and tomatoes. And sorry, but I can’t resist that pointing out that one of Khodadad’s colleagues is called Matthew Romeyn.

For the past few months astronomers have been excitedly watching the nearby star Betelgeuse in anticipation of its explosion. The reason is that the star had been dimming since about the middle of October, which suggested that it could become a supernova. That dimming has since stopped and it now appears that the star is getting brighter – so possibly bad news if you were looking forward to a spectacular explosion.

Emily Levesque of the University of Washington and colleagues have now put forth the theory that Betelgeuse had dimmed because it expelled matter from its surface and this “dust” blocked some starlight. You can find out more in “Dimming Betelgeuse likely isn’t cold, just dusty, new study shows”.

Mars rover launch delayed until 2022

Europe’s Rosalind Franklin rover, which was set to begin its journey to Mars this summer, has had its launch postponed until 2022 amid parachute and electronics difficulties and uncertainty created by the COVID-19 pandemic.

The joint mission between the European Space Agency (ESA) and the Russian space agency Roscosmos, which is designed to seek out evidence of past life on Mars, has already experienced numerous delays during its long development. This latest postponement has been on the cards since tests of the rover’s parachute system, which is designed to safely land the spacecraft on Mars, ended in failure in August 2019.

“We’ve been racing against time in terms of getting everything ready,” says David Parker, director of human and robotic exploration at ESA. “And now we have the coronavirus issue, which is the straw that broke the camel’s back.”

During a meeting between the hierarchies of ESA and Roscosmos, officials decided to delay the launch to allow time for the problems to be fixed. The orbital dynamics of Earth and Mars mean that launch windows only open for a few weeks every two years, to take advantage of the two planets’ closest approach to one another. The mission will now launch sometime between August and October 2022, reaching Mars by April 2023 at the earliest.

A series of glitches

The problem with the parachutes is not the parachutes themselves, but the way that they deploy from inside their protective bags. “They are packed incredibly tightly,” says Parker. “It’s almost a dark art how they are packed.”

During previous “drop-tests”, the main 15m and 35m parachutes developed large tears as they deployed. This prompted a redesign of the protective bags, and two more drop-tests are scheduled for the end of March in the US. However, as coronavirus spreads and travel bans are put in place, these crucial tests are unlikely to happen in time.

A parachute dangling from a gantry above a testing centre — **Trial run** Tests on the rover’s parachute bags revealed a need to redesign the system to prevent damage to the parachutes. (Courtesy: NASA/JPL–Caltech)

Further complicating matters are troublesome glitches in the electronics units within the Russian lander, Kazachok, which will deploy Rosalind Franklin onto the surface and will carry 13 science instruments of its own. “One of the units will probably have to go back to Russia to be fixed,” says Parker. He adds that the current 14-day quarantine rules in place in Russia make it difficult for teams from Russia and European countries to be in the same place at the same time.

For the rover’s developers, it’s a frustrating, if understandable, development. Andrew Coates, who leads the science team on the rover’s panoramic camera (PanCam), points out that the extra time can be spent performing more simulations of how the rover will perform, with all nine instrument teams involved.

“This will still be a cutting-edge science mission in 2023, as it’s the only mission drilling two metres underneath the harsh surface of Mars and looking for biomarkers and life,” says Coates, a physicist in the Mullard Space Science Laboratory at University College London, UK. “We now just need to wait a bit longer.”

Rossby waves on the Sun provide a tool for forecasting space weather

Weather conditions on Earth are influenced by a phenomenon known as Rossby waves. These planetary-scale fluctuations arise because the Coriolis force – due to the Earth’s rotation – varies with latitude. The resulting pressure system is associated with the jet stream in the atmosphere and also helps govern currents in the oceans.

Within the past decade, Rossby waves have also been observed within the atmosphere of the Sun. While the Earth’s Rossby waves are purely hydrodynamic, the Sun’s Rossby waves are also influenced by the strong magnetic fields at the Sun’s outer layers. In this video interview, space scientist Mausumi Dikpati introduces solar Rossby waves and explains how they can be used to predict space weather, which can pose a threat to the Earth.

Dikpati is a senior scientist at the High Altitude Observatory, a laboratory of the US National Center for Atmospheric Research in Boulder, Colorado. She studies the dynamics between Rossby waves and solar activity such as flares and coronal mass ejections (CMEs). Developing a clear understanding of these processes could lead to mid-term space weather predictions.

Diamond micro-lenses stand up to synchrotron sources

An international team of researchers has produced a stack of diamond micro-lenses precise enough to be compatible with the latest generation of X-ray sources. Physicists led by Polina Medvedskaya at Immanuel Kant Baltic Federal University in Russia developed the intricate structures using ion-beam lithography – a novel approach that could open up new opportunities for compact X-ray microscopy.

Today’s “fourth generation” synchrotrons produce high-quality beams of X-rays that are ideal for imaging. However, advances in the lenses used to shape and condition X-rays have not kept pace with advances in synchrotron technology. When powerful X-ray beams interact with even nanoscale imperfections in lenses, the resulting aberrations fundamentally limit the resolution of the resulting images. This makes it difficult to fully exploit the advantages of modern synchrotrons for X-ray microscopy.

Medvedskaya’s team suggest that this problem could be solved using lenses made from diamond, which has a continuous structure that limits any graininess in the images produced. In addition, the material’s high thermal conductivity and resistance to change at high temperatures would make these lenses able to better withstand intense, high-energy X-ray beams. Furthermore, diamond’s high refractive index means that the optical setup could be more compact than is the case for commonly-used metal and polymer lenses.

Compact stacks of lenses

To create their high-quality lenses, the researchers used beams of ions less than 5 nm in diameter to carve out the lens shapes. This ion-beam lithography technique is commonly used to etch circuits and other high-resolution patterns onto 3D surfaces, and it enabled Medvedskaya and colleagues to produce sets of three diamond half-lenses with curvature radii of just 4.8 µm. They then assembled the lenses into compact stacks using micro-manipulation.

Images of the lenses obtained through scanning electron microscopy revealed that they each had a surface roughness no larger than 30 nm, and an overall curvature accurate to within just 200 nm. In tests at the PETRA-III synchrotron X-ray source at DESY in Germany, Medvedskaya and colleagues used their lenses to focus the hot, intense beams produced by the source down to resolutions of 100 nm.

With further research, the team say their approach could significantly improve the capabilities of modern synchrotron sources, enabling researchers to produce nanoscale-resolution images using a durable, highly compact apparatus. This would be particularly useful for phase-contrast imaging, which exploits differences in the refractive indexes of different materials to precisely differentiate between their structures. If the lens production technique becomes widely adopted, Medvedskaya and colleagues believe it could create diverse new opportunities for research in areas that require reliable shaping and conditioning of X-ray beams.

PET scans could help develop shorter TB treatments

Shortening tuberculosis (TB) treatment by optimizing antibiotic dosing may be possible using data acquired from PET/CT scans. In a first-in-human study, scientists successfully measured antibiotic concentration–time profiles in patients with pulmonary TB, an important first step towards the use of PET scans as a tool to optimize TB treatment (Nature Med. 10.1038/s41591-020-0770-2).

Treatment of TB typically requires the patient to take prescription drugs for six or more months. Currently, the typical daily dose of rifampin, a first-line TB drug, is 10 mg/kg; but doses of up to 35 mg/kg per day are safe in adults. Higher drug concentrations at infection sites could more effectively kill pathogens, making treatments shorter, and reducing the risk of failure, relapse and death.

Effective treatment of infections depends upon achieving adequate levels of the antibiotic at the infection sites, where the microbes reside. However, due to the difficulties of directly sampling infected tissues, information on rifampin levels at infection sites has only been available from TB patients with refractory disease, where resections are performed to remove the infected areas.

Principal investigator Sanjay Jain and lead author Alvaro Ordonez, of the Center for Tuberculosis Research at Johns Hopkins University School of Medicine, overcame this challenge using PET/CT with¹¹C-rifampin, a radiolabelled analogue of rifampin. They acquired area under the concentration–time curve (AUC) data from microdose dynamic ¹¹C-rifampin PET/CT scans. The PET data were then used to determine concentration–time profiles of rifampin at infection sites, which provided a “translational bridge” allowing for pharmacodynamic modelling, according to the authors.

The team performed a multi-institutional study in 12 patients (nine men and three women, aged 19 to 77 years) newly diagnosed with rifampin-susceptible pulmonary TB. Half of the patients had pulmonary cavitation, thick-walled abnormal spaces in the lung, and all had been receiving treatment for at least 10 days prior to their PET/CT scan. The researchers made a total of 1221 measurements, including 473 from infected lung lesions and 748 from uninfected areas including the lung, brain, liver and plasma.

The researchers used the PET data to calculate the tissue-to-plasma AUC ratio for each pathologically distinct lesion using a plasma pharmacokinetics model. The model described the distribution of ¹¹C-rifampin into affected and unaffected lung regions using the concentration–time profiles obtained from the PET data. CT results showed that pulmonary lesions were heterogeneous in different lung regions of a patient. ¹¹C-rifampin exposures in pulmonary TB lesions were low, spatially compartmentalized and demonstrated between- and within-patient variability. The ¹¹C-rifampin AUC tissue-to-plasma ratios were lowest in cavity walls, compared with other TB lesions or unaffected lung.

“This was eye-opening, since cavities are known to harbour the largest number of mycobacteria within infected lungs,” said Ordonez. “Cavitary TB patients are also more likely to fail treatment and spread the disease to other individuals. Rifampin is not getting where we need it most.”

To confirm the human findings, the team performed ¹¹C-rifampin PET/CT on rabbits infected with cavitary TB that closely replicates human pathology, before and after 30–50 days of anti-TB treatment. The PET/CT images also demonstrated limited and spatially compartmentalized ¹¹C-rifampin exposure in TB lesions, with the lowest levels in cavity walls. Post-mortem mass spectrometry in these infected rabbits showed a similar trend to the PET data.

The researchers used the PET data to develop an integrated pharmacokinetics model to predict the ¹¹C-rifampin plasma and tissue concentrations in all patients, and the intra-lesional drug exposure in patients who received daily oral rifampin doses of 10–50 mg kg. With these data, they were able to predict accelerated cure rates based on different rifampin doses. Their results suggest that increasing the dose of rifampin to higher, yet safely tolerated levels, could reduce the treatment course in most TB patients from six to four months.

“This non-invasive approach to measure intralesional pharmacokinetics of antibiotics can also be used in other infections like methicillin-resistant Staphylococcus aureus, or MRSA, which is often treated with long courses of rifampin” Jain says. “We would finally be able to determine the most effective doses of specific drugs in specific patients.”

American Physical Society cancels April Meeting due to coronavirus pandemic

The American Physical Society’s April Meeting has become the latest event in the scientific calendar to be cancelled due to the coronavirus pandemic. The annual particle-physics gathering, which was scheduled to take place in Washington, DC, on 18-21 April, has been called off, with organizers working to set up an online “virtual” meeting in its place.

The announcement came less than 24 hours after DC mayor Muriel Bowser declared both a state of emergency and a public health emergency in the US capital, which has so far reported 10 cases of the novel coronavirus amid widespread reports of testing kits being unavailable or in limited supply. Tours of major public buildings in Washington – including the US Capitol – have been suspended, and schools in neighbouring Loudon County, Virginia have been closed in an effort to limit the virus’ spread.

In a statement, the APS cited concerns for “the health and well-being of its members, attendees, and staff” as well as the local community as reasons for the cancellation. Other factors included the World Health Organization’s 11 March decision to characterize COVID-19 as a pandemic and recommendations that communities adopt “social distancing” measures to reduce the epidemic’s speed and severity.

Details of the planned “virtual” meeting were not immediately available, but there is a growing precedent for such events within the physics community. After the APS March Meeting, which focuses on condensed-matter physics, was cancelled earlier this month, a group of would-be attendees set up a “virtual meeting” website. As of 12 March, some 150 talks had been uploaded to the website, which by then had 8000 users and received 50,000 page views. The American Association of Physicists in Medicine has also elected to turn its spring clinical meeting – which had been scheduled to take place in Minneapolis, Minnesota on 4-7 April – into a virtual event.

Participants who registered to attend the APS April Meeting will receive a refund of their fees. An official letter of cancellation is also available to help registrants cancel or claim back the cost of flights and accommodation. More information is available here.

3D nano-vortices come into view

Vortices, domain walls and other magnetic phenomena behave in complex and dynamic ways, but limitations in imaging technology have so far kept researchers from observing them in more than two dimensions. Scientists in the UK and Switzerland have now found a way around this obstacle. According to physicist Claire Donnelly, who led the effort together with colleagues at the University of Cambridge, ETH Zurich and the Swiss Light Source, their new technique will give physicists a deeper understanding of how 3D magnetic materials work and how to harness them for future applications.

Changes in a material’s magnetization take place on the nanoscale in both time and space. Measuring these tiny, rapidly changing details is challenging, so scientists generally limit their studies to flat samples. While three-dimensional imaging has been recently demonstrated using techniques such as X-ray, neutron and electron tomography, the images obtained are static and do not show how the magnetic structures evolve over time.

One reason it is hard to capture magnetization changes in three dimensions is that the magnetization can point in any direction. This means that, when studying a 3D sample of magnetic material, the sample’s orientation with respect to its rotation axis needs to be changed partway through the measurement in order to measure all three spatial components (x,y,z) of the magnetization.

High-energy X-ray probe

That’s not easy to do, so Donnelly and colleagues instead used short, fast pulses of high-energy synchrotron X-rays to probe the magnetic state of a 3D magnetic structure (a microdisc of gadolinium cobalt, in this case) in different directions. This technique, which the team have dubbed time-resolved magnetic laminography, enabled them to measure how the magnetic state evolves in response to an alternating applied oscillating magnetic field, which the researchers synchronized to the frequency of the X-ray pulses.

Thanks to a specially-developed reconstruction algorithm, the team obtained a seven-dimensional dataset of measurements: three dimensions for the position of the magnetization state, three for its direction and one for time. The result is, in effect, a map of the magnetization dynamics for seven different time steps evenly spaced over 2 ns, with a temporal resolution of 70 picoseconds and a spatial resolution of 50 nanometres.

In some ways, Donnelly says the team’s approach is similar to computer tomography (CT), which is widely employed for 3D imaging in many areas, including CT scans in hospitals. Laminography involves measuring 2D projections of the magnetic structure for a number of different orientations of the sample. Importantly, the axis of rotation of the microdisc being measured is not perpendicular to the X-ray beam, so the team was able to access all three spatial components of the magnetization direction.

Towards a new generation of technological devices

The researchers visualized two main types of magnetization dynamics in their experiments: the 3D motion of magnetic vortices moving back and forth; and the precession of the magnetization vector. The movement of such structures had previously only been observed in two dimensions.

Doughnut-shaped nanomagnets induce new magnetization states

The new technique could help researchers better understand magnetic materials, Donnelly says. Well-known structures such as permanent magnets and inductive materials – both widely employed in sensing and energy production – could be studied with a view to improving their performance. Donnelly adds that there is also a growing interest in 3D magnetic nanostructures, which are predicted to have completely new properties and functionalities hard to achieve in their 2D counterparts. As well as providing insights into the physics of phenomena such as ultra-high domain wall velocities and magneto-chiral effects, these nanostructures might form the basis of a new generation of technological devices, boosting information transfer rates and data storage densities.

“This is a very exciting area of research,” she tells Physics World. “With our new technique, the magnetic materials community will now be able to measure and understand these systems – and hopefully exploit their properties.”

The research is described in Nature Nanotechnology.

‘Super-puff’ exoplanets put a ring on it

The apparent “puffiness” of some exoplanets could be due to Saturn-like rings, rather than envelopes of gas as was previously thought. That’s the view of astronomers Anthony Piro at the Carnegie Institution for Science and Shreyas Vissapragada at the California Institute of Technology, US, who came to this conclusion after simulating the transits of several “super-puff” exoplanets. Their analysis exposes two such exoplanets as likely candidates for having rings – a finding that could be confirmed after the upcoming launch of the James Webb Space Telescope (JWST).

As the list of known exoplanets expands, astronomers are identifying a growing number of bodies that appear to have remarkably large radii, given their relatively low masses. Nicknamed “super-puffs”, these seemingly ultra-low-density planets are typically anomalously cool, and are found in star systems with widely varying ages – meaning that most of them probably aren’t just young planets that haven’t yet fully formed.

To explain these enigmatic objects, some astronomers have proposed that they are surrounded by thick envelopes of gas. If this were the case, these envelopes could be expected to leave diverse absorption dips in the spectra of starlight passing through them. However, the super-puff spectra observed so far have been frustratingly featureless.

Not so puffy

Piro and Vissaptragada propose a different explanation. In their view, super-puffs aren’t actually puffy, but are instead surrounded by rings. These rings dim the light of the planets’ host stars as they pass between the star and observers on Earth, creating the illusion of exoplanets with far larger radii. They tested this theory by simulating observations of Saturn transiting the Sun, from the perspective of a distant star system. This revealed that Saturn would appear to be half as dense as it actually is if its rings weren’t accounted for.

The duo also simulated the transits of a variety of known super-puffs, aiming to determine whether the transit observations could have been distorted by rings. They found that their hypothesis was consistent with the transits of some exoplanets, but not all of them: given their proximity to their host stars, many of the bodies would need to have heavier, rocky rings instead of ice, which would limit the rings’ radii. In addition, the planets would need to spin fast enough to prevent warping in their rings – but this is often hindered by tidal locking with host stars.

These effects didn’t rule out every planet the duo considered. Of the exoplanets they analysed, Piro and Vissaptragada concluded that Kepler 87c and 177c have the best chance of appearing puffy due to rings. Confirming this will require more accurate photometric techniques than are currently available, but these improved measurements should be within reach of the long-awaited JWST, which is now scheduled for launch in March 2021. If such predictions are confirmed, they could greatly improve astronomers’ understanding of how planetary systems form and evolve.

Low-dose chest CT doesn’t appear to damage DNA

Immunofluorescent staining showing γ-H2AX foci in blood lymphocytes following standard-dose CT. Left: nuclear DNA of four lymphocytes. Centre: γ-H2AX foci. Right: markers of DNA double-strand breaks; DNA is blue and γ-H2AX foci are red. Scale bar: 5 µm. (Courtesy: RSNA)

Early detection and treatment of lung cancer are essential to reduce the mortality rate. According to the National Lung Screening Trial, screening high-risk patients with low-dose chest CT can reduce deaths from lung cancer compared with screening with chest X-rays. However, although low-dose CT delivers about one quarter the radiation dose of standard CT, its biologic effects remain unclear.

To investigate whether exposure to low-dose CT could increase the risk of radiation-induced cancers, a Japanese research team compared the number of DNA double-strand breaks and chromosome aberrations in peripheral blood lymphocytes following low-dose and standard-dose chest CT. They found that the low-dose CT scans used in lung cancer screening did not appear to damage human DNA (Radiology 10.1148/radiol.2020190389)

The study included 209 participants referred for chest CT studies, 107 of whom underwent low-dose CT and 102 who had standard-dose CT. The median effective dose was 1.5 mSv for low-dose CT and 5.0 mSv for standard-dose CT, with blood doses approximately 30% lower after low-dose CT than standard-dose CT. The researchers – from Hiroshima University and Fukushima Medical University – took peripheral blood samples from all participants immediately before and 15 minutes after the CT exam, and analysed blood lymphocytes in the samples.

To count the number of DNA double-strand breaks after CT, the researchers used immunofluorescent staining to visualize γ-H2AX, a marker of DNA double-strand breaks. They counted γ-H2AX foci in blood samples from 101 patients who underwent low-dose CT and 101 who had standard-dose CT. Before scanning, the median number of foci was similar in both groups. After CT, the median number of γ-H2AX foci showed a significant increase in the standard-dose group (from 0.11 to 0.16 foci per cell), while no significant increase was observed in low-dose CT group (from 0.15 to 0.17 foci per cell).

The team also quantified the number of chromosome aberrations, which reflect both the radiation damage and the accuracy of DNA repair, in 95 low-dose CT and 92 standard-dose CT patients. The median numbers of chromosome aberrations before low-dose and standard-dose CT were 6.7 and 7.6 per 1000 metaphases, respectively. After CT, the number of chromosome aberrations per 1000 metaphases was 7.2 in the low-dose group and 9.7 for the standard-dose group.

To confirm this finding that standard-dose CT resulted in greater DNA damage than low-dose CT, the researchers studied 63 individuals who underwent both low- and standard-dose CT. The number of cells collected enabled analysis of γ-H2AX and chromosome aberrations in 57 and 54 participants, respectively.

After low-dose CT, the number of γ-H2AX foci per cell increased from 0.11 to 0.16, while the number of chromosome aberrations per 1000 metaphases grew from 7.1 to 8.0. After standard-dose CT, the number of foci increased from 0.11 to 0.20, and the number of chromosome aberrations increased from 7.8 to 9.2.

“We could clearly detect the increase of DNA damage and chromosome aberrations after standard chest CT,” says senior author Satoshi Tashiro from Hiroshima University. “In contrast, even using these sensitive analyses, we could not detect the biological effects of low-dose CT scans. This suggests that application of low-dose CT for lung cancer screening is justified from a biological point of view.”

Harnessing the power of the oceans, careers tips, and a close look at terahertz technologies

In this episode of the Physics World Weekly podcast, we delve into the March 2020 edition of Physics World magazine, taking a look at a feature examining how scientists hope to harness power from the motion of ocean waves, plus the magazine’s new interview-based graduate careers advice section.

We also talk about some of the many applications of terahertz waves, including ghost imaging, speeding communications networks and searching for the origins of life on Earth.

Finally, we discuss how – in the light of increasing travel bans and restrictions on large gatherings – some conference organizers are looking to transition their scientific meetings from physical to virtual events.

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If conferences did post-talk analysis interviews, space lettuce is on the menu, dimming Betelgeuse may just be dust