Tech

Cranfield-led research has assessed the initial impact of COVID-19 on air transport and found that it is likely to lead to a smaller, consolidated sector in the future.

The research - involving a series of in-depth interviews with senior aviation industry executives along with analysis of flight and air freight data - provides an early assessment of the medium- and long-term impact of COVID-19 on air transport for both passenger and cargo traffic.

After a rapid geographical spread of the virus with initial manifestation in Asia and a lagged response in the rest of the world, most airlines tried to operate a normal schedule until they were prevented by mobility restrictions such as border closures and lockdowns, translating into sudden drops in flight numbers from mid-March.

Data showed that impact has been stronger in international than domestic markets. There was a partial recovery of Asia Pacific domestic markets during March, fueled by China's recovery, turning into a double-dip in April as other Asian countries experienced drops in domestic traffic in line with global trends.

Interviewees thought the crisis would lead to consolidation and a significantly smaller industry and were concerned about the possible differences in state aid and how that could affect the level playing field in a post-COVID-19 aviation market.

Dr Pere Suau-Sanchez, Senior Lecturer in Air Transport Management at Cranfield University, said: "Along with other sectors of the economy, air traffic is vulnerable to external factors, such as oil crises, natural disasters, armed conflicts, terrorist attacks, economic recessions and disease outbreaks. The findings of this paper represent an early assessment that can help the aviation industry and other related industries like tourism in the preparation for the recovery period.

"We focused on identifying aspects that can structurally redefine the aviation industry in the medium and long term for both passenger and cargo traffic, particularly around supply and demand, traffic resilience, passenger behaviour, health regulations and business ethics. Understanding these structural elements in an integrated way can provide more confidence in efforts to predict the future context. As the views of senior stakeholders might change as the crisis evolves, a record of their early assessments also represents a valuable reference for future analysis."

Other COVID-19 consequences highlighted by the interviewees included:

Full-service network carriers (FSNCs) are likely to be major losers since the recovery in international markets will be slower and they may face new competition with the potential entry of new airlines in their home hub markets.

Regional airlines were identified as possible short-term winners during the recovery period as they could potentially help FSNCs adjust their feeding capacity.

Low-cost carriers are expected to concentrate in primary markets with possible entry in hub airports, and a general reduction in frequencies at the route level.

Regional and secondary airports are likely to lose out as capacity is freed up in larger markets, attracting airlines and enabling larger hub airports to reinforce their positions.

Interviewees were concerned about the recovery of business travel, mainly due to the cancellation of meetings, incentives, conferencing and exhibitions (MICE) events, and the uneven lift of travel bans. Teleworking was seen as a serious threat to demand, with the current context of digital transformation and cloud apps offering better solutions for teleworking than the traditional videoconference.

The recuperation of the leisure passenger segment was expected to be quicker but reduced disposable incomes would curtail propensity to fly and require significant support, such as route subsidies. Fear and health concerns were identified as major issues for the leisure traveller, more so than for the business traveller.

In regulatory terms, all interviewees believed that new health screening controls would be imposed at airports, translating into higher costs for airports and passengers, but did not consider social distancing to be a viable commercial option for airlines.

The interviews also identified areas in which the industry could be transformed towards a more ethical business, for example around supply chains and more responsible consumption.

Interviews with 16 managers from across the airline and airport sectors (including major, low-cost and regional carriers, large hub, medium and regional airports, a pilots' union and an aviation insurance broker) were conducted between 19 March and 17 April. Global flight supply and air freight data, including origin and destination airport, time of departure and arrival, number of seats supplied, aircraft type, and day of operation was analysed for the first four months of 2020.

The full paper - An early assessment of the impact of COVID-19 on air transport: Just another crisis or the end of aviation as we know it? - published in the Journal of Transport Geography, and co-authored with Augusto Voltes-Dorta, University of Edinburgh Business School, and Natàlia Cugueró-Escofet, Universitat Oberta de Catalunya.

Researchers around the world are working on ways to transfer data in the terahertz (THz) range, which would make it possible to send and receive information much faster than what is allowed by today's technology. But the issue they're facing is that it is much more difficult to encode data in the THz range than in the GHz range, which is currently used by 5G tech. A group of scientists from ITMO University have demonstrated the possibility of modifying terahertz pulses in order to use them for data transmission. An article on this subject was published in Scientific Reports.

Telecommunications companies in advanced economies are beginning to adopt the new 5G standard, which will endow users with previously-unseen wireless data transfer speeds. Meanwhile, as the world makes its first steps towards this new generation of data networks, scientists are already at work on its successor. "We're talking about 6G technologies," says Egor Oparin, a staff member of ITMO University's Laboratory of Femtosecond Optics and Femtotechnologies. "They will increase data transfer speeds by anywhere from 100 to 1,000 times, but implementing them will require us to switch to the terahertz range."

Today, a technology for simultaneous transfer of multiple data channels over a single physical channel has been successfully implemented in the infrared (IR) range. This technology is based on the interaction between two broadband IR pulses with a bandwidth measured in tens of nanometers. In the terahertz range, the bandwidth of such pulses would be much larger - and so, in turn, would be their capacity for data transfer.

But before we begin to consider 6G technology, scientists and engineers will need to find solutions to numerous crucial issues. One such issue has to do with ensuring the interference of two pulses, which would result in a so-called pulse train or frequency comb used to encode data.

"In the terahertz range, pulses tend to contain a small number of field oscillations; literally one or two per pulse," says Egor Oparin. "They are very short and look like thin peaks on a graph. It is quite challenging to achieve interference between such pulses, as they are difficult to overlap."

A team of scientists at ITMO University has suggested extending the pulse in time so that it would last several times longer but still be measured in picoseconds. In this case, the different frequencies within a pulse would not occur simultaneously, but follow one another in succession. In scientific terms, this is referred to as chirping or linear-frequency modulation. However, it comes with another challenge: although chirping technologies are quite well-developed in regards to the infrared range, there is a lack of research on the technique's use in the terahertz range.

"We've turned to the technologies used in the microwave range," says Egor Oparin, who is a co-author of the paper.

"They actively employ metal waveguides, which tend to have high dispersion, meaning that different emission frequencies propagate at different speeds there. But in the microwave range, these waveguides are used in single mode, or, to put it differently, the field is distributed in one configuration, in a specific, narrow frequency band, and, as a rule, in one wavelength. We took a similar waveguide of a size suitable for the terahertz range and passed a broadband signal through it so that it would propagate in different configurations; because of this, the pulse became longer in duration, changing from two to about seven picoseconds, which is three and a half times more. This became our solution."

By using a waveguide, researchers have been able to increase the length of the pulses to a duration that is necessary from a theoretical standpoint. This made it possible to achieve interference between two chirped pulses that together create a pulse train. "What's great about this pulse train is that it exhibits a dependence between a pulse's structure in time and the spectrum," says the scientist. "So we have temporal form, or simply put field oscillations in time, and spectral form, which represents those oscillations in the frequency domain. Let's say we've got three peaks, three substructures in the temporal form, and three corresponding substructures in the spectral form. By using a special filter to remove parts of the spectral form, we can "blink" in the temporal form and the other way around. This could be the basis for data encoding in the terahertz band."

NEW YORK, June 10, 2020 -- A research team led by scientists at the Advanced Science Research Center at The Graduate Center, CUNY (CUNY ASRC), in collaboration with National University of Singapore, University of Texas at Austin and Monash University, has employed "twistronics" concepts (the science of layering and twisting two-dimensional materials to control their electrical properties) to manipulate the flow of light in extreme ways. The findings, published in the journal Nature, hold the promise for leapfrog advances in a variety of light-driven technologies, including nano-imaging devices; high-speed, low-energy optical computers; and biosensors.

The team took inspiration from the recent discovery of superconductivity in a pair of stacked graphene layers that were rotated to the "magic twist angle" of 1.1 degrees. In this configuration, electrons flow with no resistance. Separately, each graphene layer shows no special electrical properties. The discovery has shown how the careful control of rotational symmetries can unveil unexpected material responses.

The research team discovered that an analogous principle can be applied to manipulate light in highly unusual ways. At a specific rotation angle between two ultrathin layers of molybdenum trioxide, the researchers were able to prevent optical diffraction and enable robust light propagation in a tightly focused beam at desired wavelengths.

Typically, light radiated from a small emitter placed over a flat surface expands away in circles very much like the waves excited by a stone that falls into a pond. In their experiments, the researchers stacked two thin sheets of molybdenum trioxide -- a material typically used in chemical processes -- and rotated one of the layers with respect to the other. When the materials were excited by a tiny optical emitter, they observed widely controllable light emission over the surface as the rotation angle was varied. In particular, they showed that at the photonic magical twist angle the configured bilayer supports robust, diffraction-free light propagation in tightly focused channel beams over a wide range of wavelengths.

"While photons -- the quanta of light -- have very different physical properties than electrons, we have been intrigued by the emerging discovery of twistronics, and have been wondering if twisted two-dimensional materials may also provide unusual transport properties for light, to benefit photon-based technologies," said Andrea Alù, founding director of the CUNY ASRC's Photonics Initiative and Einstein Professor of Physics at The Graduate Center. "To unveil this phenomenon, we used thin layers of molybdenum trioxide. By stacking two of such layers on top of each other and controlling their relative rotation, we have observed dramatic control of the light guiding properties. At the photonic magic angle, light does not diffract, and it propagates very confined along straight lines. This is an ideal feature for nanoscience and photonic technologies."

"Our discovery was based on quite a specific material and wavelength range, but with advanced nanofabrication we can pattern many other material platforms to replicate these unusual optical features over a wide range of light wavelengths," said National University of Singapore (NUS) graduate student Guangwei Hu, who is first author of the study and a long-term visiting researcher with Alù's group. "Our study shows that twistronics for photons can open truly exciting opportunities for light-based technologies, and we are excited to continue exploring these opportunities," said Prof. C.W. Qiu, Mr. Hu's co-advisor at NUS.

Researchers have identified two brain phenomena that may explain some of the side-effects of ketamine. Their measurements of the brain waves of sheep sedated by the drug may explain the out-of-body experience and state of complete oblivion it can cause.

In a study aimed at understanding the effect of therapeutic drugs on the brains of people living with Huntington's disease, researchers used electroencephalography (EEG) to measure immediate changes in the animals' brain waves once ketamine - an anaesthetic and pain relief drug - was administered. Low frequency activity dominated while the sheep were asleep. When the drug wore off and the sheep regained consciousness, the researchers were surprised to see the brain activity start switching between high and low frequency oscillations. The bursts of different frequency were irregular at first, but became regular within a few minutes.

"As the sheep came round from the ketamine, their brain activity was really unusual," said Professor Jenny Morton at the University of Cambridge's Department of Physiology, Development and Neuroscience, who led the research. "The timing of the unusual patterns of sheep brain activity corresponded to the time when human users report feeling their brain has disconnected from their body."

She added: "It's likely that the brain oscillations caused by the drug may prevent information from the outside world being processed normally,"

The findings arose as part of a larger research project into Huntington's disease, a condition that stops the brain working properly. The team want to understand why human patients respond differently to various drugs if they carry the gene for this disease. Sheep were used because they are recognised as a suitable pre-clinical model of disorders of the human nervous system, including Huntington's disease.

Six of the sheep were given a single higher dose of ketamine, 24mg/kg. This is at the high end of the anaesthetic range. Initially, the same response was seen as with a lower dose. But within two minutes of administering the drug, the brain activity of five of these six sheep stopped completely, one of them for several minutes - a phenomenon that has never been seen before.

"This wasn't just reduced brain activity. After the high dose of ketamine the brains of these sheep completely stopped. We've never seen that before," said Morton. Although the anaesthetised sheep looked as though they were asleep, their brains had switched off. "A few minutes later their brains were functioning normally again - it was as though they had just been switched off and on."

The researchers think that this pause in brain activity may correspond to what ketamine abusers describe as the 'K-hole' - a state of oblivion likened to a near-death experience, which is followed by a feeling of great serenity. The study is published today in the journal Scientific Reports.

Ketamine abusers are known to take doses many times higher than those given to the sheep in this research. It is also likely that progressively higher doses have to be taken to get the same effect. The researchers say that such high doses can cause liver damage, may stop the heart, and be fatal.

To conduct the experiment sheep were put into veterinary slings, which are commonly used to keep animals safe during veterinary procedures. Different doses of ketamine were given to 12 sheep and their brain activity recorded with EEG.

Ketamine was chosen for the study because it is widely used as a safe anaesthetic and pain-relief drug for treating large animals including dogs, horses and sheep. It is also used medically, and is known as a 'dissociative anaesthetic' because patients can appear awake and move around, but they don't feel pain or process information normally - many report feeling as though their mind has separated from their body.

At lower doses ketamine has a pain-relieving effect, and its use in adult humans is mainly restricted to field situations such as frontline pain-relief for injured soldiers or victims of road traffic accidents.

"Our purpose wasn't really to look at the effects of ketamine, but to use it as a tool to probe the brain activity in sheep with and without the Huntington's disease gene," said Morton. "But our surprising findings could help explain how ketamine works. If it disrupts the networks between different regions of the brain, this could make it a useful tool to study how brain networks function - both in the healthy brain and in neurological diseases like Huntington's disease and schizophrenia."

Ketamine has recently been proposed as a new treatment for depression and post-traumatic stress disorder. Beyond its anaesthetic actions, however, very little is known about its effects on brain function.

"We think of anaesthetic drugs as just slowing everything down. That's what it looks like from the outside: the animals basically go to sleep and are unresponsive, and then they wake up very quickly. But when we looked at the brain activity, it seems to be a much more dynamic process," said Morton.

Scientists from the University of Cambridge, in collaboration with the Hubrecht Institute in The Netherlands, have developed a new model to study an early stage of human development, using human embryonic stem cells. The model resembles some key elements of an embryo at around 18-21 days old and allows the researchers to observe the processes underlying the formation of the human body plan never directly observed before. Understanding these processes holds potential to reveal the causes of human birth defects and diseases, and to develop tests for these in pregnant women.

The body plan, or blueprint of an organism, arises through a process called 'gastrulation'. During gastrulation, three distinct layers of cells are formed in the embryo that will later give rise to all the body's major systems: the ectoderm will make the nervous system, mesoderm the muscles, and endoderm the gut.

Gastrulation is often referred to as the 'black box' period of human development, because legal restrictions prevent the culture of human embryos in the lab beyond day 14, when the process starts. This limit was set to fall at the stage where the embryo can no longer form a twin.

Many birth defects originate during this 'black box' period, with causes including alcohol, medications, chemicals and infections. A better understanding of human gastrulation could also shed light on many medical issues including infertility, miscarriage, and genetic disorders.

"Our model produces part of the blueprint of a human," said Professor Alfonso Martinez-Arias from the University of Cambridge's Department of Genetics, who led the study. "It's exciting to witness the developmental processes that until now have been hidden from view - and from study."

Published today in the journal Nature, the report describes a method of using human embryonic stem cells to generate a three-dimensional assembly of cells, called gastruloids, which differentiate into three layers organised in a manner that resembles the early human body plan.

To make gastruloids in the lab, defined numbers of human embryonic stem cells were placed in small wells, where they formed tight aggregates. After treatment with chemical signals, the gastruloids were seen to lengthen along a head to tail axis, known as the anteroposterior axis, turning on genes in specific patterns along this axis that reflect elements of a mammalian body plan.

Model organisms including mice and zebrafish have previously enabled scientists to gain some insights into human gastrulation. However, these models may behave differently to human embryos when the cells start to differentiate. Animal models can respond differently to certain drugs: the anti-morning sickness drug thalidomide, for example, passed clinical trials after testing in mice but subsequently led to severe birth defects in humans. For this reason it is important to develop better models of human development.

Gastruloids do not have the potential to develop into a fully-formed embryo. They do not have brain cells or any of the tissues needed for implantation in the womb. This means they would never be able to progress past the very early stages of development, and therefore conform to current ethical standards.

By looking at which genes were expressed in these human gastruloids at 72 hours of development, the researchers found a clear signature of the event that gives rise to important body structures such as thoracic muscles, bone and cartilage, but they do not develop brain cells.

The researchers judged the equivalent human embryonic age of the gastruloids by comparing them to the Carnegie Collection of Embryology. This official collection contains a continuum of human embryos, including day-by-day growth over the first eight weeks. They suggest that gastruloids partially resemble 18-21 day old human embryos.

"This is a hugely exciting new model system, which will allow us to reveal and probe the processes of early human embryonic development in the lab for the first time," said Dr Naomi Moris in the University of Cambridge's Department of Genetics, and first author of the report. "Our system is a first step towards modelling the emergence of the human body plan, and could prove useful for studying what happens when things go wrong, such as in birth defects."

EAST LANSING, Mich. - As policymakers increasingly turn toward science in addressing global climate change, one Michigan State University scientist is looking to nature to develop the next generation of solar energy technology.

MSU Foundation Professor James McCusker, Department of Chemistry, believes that the future of solar energy lies in abundant, scalable materials designed to mimic and improve upon the energy conversion systems found in nature.

In a groundbreaking new study in Nature, McCusker reveals a novel process that allows molecules to tell scientists how they should be modified to better absorb and convert solar energy. The method uses a molecular property known as quantum coherence where different aspects of a molecule are synchronous, like when your car's turn signal blinks in unison with that of the car in front of you. Scientists believe that quantum coherence may play a role in natural photosynthesis.

"Our work is the first time anyone has tried to actively use information gleaned from quantum coherence as a guide -- a roadmap -- to suggest what are the most important aspects of a molecule's structure that contribute to a given property," McCusker said. "We are using sophisticated science that provides the means for nature to teach us what we need to focus on in the lab."

Sunlight, although abundant, is a low-density energy source. To collect meaningful amounts of energy you need larger amounts of space. However, the most effective materials in use today for solar energy conversion, such as Ruthenium, are some of the rarest metals on Earth. Future solar technologies must be able to scale up with more efficient and cheaper methods of energy conversion.

"When I give talks about energy science at undergraduate schools or to the general public, I half-jokingly say that there are a lot of leaves on trees for a reason," McCusker said. "Well, there are a lot of leaves for a reason: Light capture is a material-intensive problem because of the (relatively) low density of energy from sunlight. Nature solves this problem by producing a lot of leaves."

Light-absorbing compounds in common synthetic methods for artificial photosynthesis make use of excited molecular states produced after a molecule absorbs energy from sunlight. The absorption of light energy exists long enough to be used in chemical reactions that rely on the ability to move electrons from one place to another. One possible solution is to find more commonly available materials that can achieve the same result.

"The problem with switching (from rare Earth metals) to something Earth-abundant like iron -- where the scalability problem disappears -- is that the processes that allow you to convert the absorbed sunlight into chemical energy are fundamentally different in these more widely available materials," McCusker said. The excited state produced by absorbing light energy in an iron-based compound, for example, decays too quickly to enable its use in a similar manner.

Enter quantum coherence as the guide. By hitting a molecule with a burst of light lasting less than one tenth of one trillionth of a second, McCusker and his students could observe the interconnection between the molecule's excited state and its structure, allowing them to visualize how the atoms of the molecule were moving during the conversion of solar to chemical energy.

"Once we had a picture of how this process occurred, the team used that information to synthetically modify the molecule in such a way as to slow the rate of the process down," McCusker said. "This is an important goal that must be achieved if these types of chromophores -- a molecule that absorbs particular wavelengths of visible light and are responsible for a material's color -- are to find their way into solar energy technologies."

"The research demonstrates that we can use this coherence phenomenon to teach us what sorts of things we might need to incorporate into the molecular structure of a chromophore that uses more earth-abundant materials to enable us to use the energy stored in the molecule upon absorption of light for a wide range of energy conversion applications."

For McCusker, this breakthrough will hopefully speed up development of new technologies, "eliminating a lot of the trial and error that goes into scientific endeavors by telling us right out of the gate what kind of system we need to design."

What next? "How about a solar cell based on paint chips and rust?" McCusker said. "We're not there yet, but the idea behind this research is to use quantum coherence to tap into information that the molecule already possesses and then use that information to change the rules of the game."

Pathogens that attack agricultural crops show remarkable adaptability to new climates and new plant hosts, new research shows.

Researchers at the Department of Biosciences, University of Exeter studied the temperature preferences and host plant diversity of hundreds of fungi and oomycetes that attack our crops.

The researchers found that plant pathogens can specialise on particular temperatures or host plants, or have wide temperature or host ranges.

Lead author Professor Dan Bebber, a member of Exeter's Global Systems Institute, said: "Traditionally, scientists have considered species to be specialists or generalists.

"Generalists are sometimes called 'Jack of all trades, master of none'. Our analyses show that many plant pathogens are 'Jack of some trades, master of others'."

Tom Chaloner, an SWBIO DTP PhD student, said: "We have collated the largest dataset on plant pathogen temperature responses, and made this available for the scientific community.

"Our data allow us to test some of the most fundamental questions in ecology and evolution.

"For example, we found that temperature preferences are narrower when pathogens are growing within plants, demonstrating the difference between the so-called fundamental niche and the realised niche."

The researchers used recently-developed statistical methods to investigate the co-evolution between pathogens and their hosts, showing that pathogens can readily evolve to attack new host plants.

"In an era of growing global population size, climate change and emerging threats to crop production and food security, our findings will be key to understanding where and when pathogens could strike next," said co-author Professor Sarah Gurr.

Some metal oxides, such as nickelates, have a tuneable resistivity, which makes them an interesting material for adaptable electronics and cognitive computing. These materials can change their nature from metallic to insulating. How exactly this metal-insulator transition takes place is a topic of great interest in condensed matter physics. However, even the metallic behaviour in nickelates seems unusual. Scientists from the University of Groningen, together with colleagues from Spain, have now found that it is not as complex as was previously assumed. The results were published on 11 June in the journal Nature Communications.

In a metal, electrons can move freely, whereas in insulators, they are strongly localized around the atomic nuclei. When a metal is heated, the ions' vibrations (called phonons) scatter the moving electrons and increase the resistivity. In contrast, heating can generate conductivity in some insulators, when electrons receive enough energy to be released and cross the energy band gap that otherwise prevents them from moving.

Exotic explanations

'In some oxides, such as nickelates, a transition from insulator to metal can occur but it is not clear how this happens,' says Beatriz Noheda, Professor of Functional Nanomaterials and Director of the Groningen Cognitive Systems and Materials Center (CogniGron) at the University of Groningen. She and her PhD student Qikai Guo are interested in nickelates because it is possible to tune their resistivity. They could be used in devices that emulate the way that synapses in our brain work.

'Before we can do this, we should understand what the nature of the simplest state, the metal state, is. This means understanding how electrons move around in the material when an electric field is applied to them,' explains Noheda. A linear change in resistivity (an exponent of 1 in the curve that represents the resistivity as a function of temperature) can be explained by a simple model in which the electrons are impeded by the vibration of the ions. 'However, for an exponent that is not 1, more exotic explanations have been suggested, based on the presence of fluctuations in the spins of the nickel electrons and electron-electron interactions that occur when the system is close to a quantum critical point.'

Strain

However, in thin films of neodymium nickelate (NdNiO3), Noheda and her team observed that the exponent was 1 in some samples, while in other samples of the same material, it was not. This suggests that the exponent is not an intrinsic property. Noheda: 'That led us to systematically look at samples grown on different substrates.' The results showed that in perfect films, the exponent is 1, which means that the resistivity is caused by phonons, as it is in normal metals. However, when the substrate that is used induces strain in the thin film, the exponent changes.

The strain leads to oxygen vacancies in the crystals and changes the forces between the ions and, therefore, the electronic energies. That, in turn, changes the materials' resistivity. 'What we found out is that we can control the number of vacancies and continuously tune the resistivity exponent at will, which is a tuning knob that we did not know we had. Thus, understanding the metal state in these nickelates may not require exotic electron-electron interactions,' Noheda concludes.

Synaptic devices

Learning how to control the metal state and the transition to the insulator state will help scientists to design electronics based on nickelates, which can emulate the way that neurons work. That is the ultimate goal of Noheda and her team. 'We now know that these nickelates are more similar to normal metals than we previously thought. This means that they can be quite good conductors if we ensure that there are no ion vacancies in the crystal. In this way, the transition to the insulating phase brings about larger changes in resistance, leading to synaptic devices with improved plasticity.'

In these experiments, the change in resistivity in these nickelates was induced by an increase in temperature. 'This is of course not ideal when you want to make a device. Our next step is to design the material in such a way that we can tune resistivity using an electric field,' Noheda concludes.

As farmers across the globe look to grow food more sustainably – with less water, fertilizer, pesticides and other environmental impacts – the use of cover crops is becoming more popular. These crops, which are often grasses or legumes, but also many other types of plants, are generally grown between the harvest and planting season of the land’s main cash crop, to reduce erosion, build soil fertility and control weeds, among other benefits. Their use has jumped in recent years. From 2012 to 2017, U.S. cover crops increased to 6.2 million hectares, an increase of 50 percent.

But the growth in cover cropping may soon hit a ceiling: planting millions of acres of cover crops will require huge extensions of land to produce cover crop seed. Between 3 and 6 percent of the 92 million acres of cropping land currently used for corn (maize) in the U.S. may be required to produce cover crop seed for that land area.

Researchers estimated that range based on 18 cover crops currently used on corn farmlands. The study was published June 11 in Communications Biology, a Nature journal, by scientists at the University of Minnesota, University of Southern California, Saint Louis University, University of Hawaii, and the Alliance of Bioversity International and CIAT.

“Cover cropping works,” said Colin Khoury, a crop researcher at the Alliance, who co-authored the study. “But it’s not yet commonly used even though it’s widely praised.”

Despite its growing popularity, only 1.7 percent of U.S. cropland currently employs cover crops. Universities, nonprofits and industry are driving growth in cover crop use through research, advocacy and education.

Cover crops make soil healthier – they reduce erosion and help restore nutrients and carbon, and create the conditions where soil can better hold moisture, all of which can help mitigate climate change as well as support farmers’ adaptation of their crops to hotter and drier conditions. They help control weeds and pests and can reduce the use of pesticides and chemical fertilizers, which have highly valued downstream benefits.

“Water quality improvements are seen quite rapidly when you use cover crops,” said Michael Kantar, a plant breeder at the University of Hawaii.

Without investment in improving cover crops, the land needed to produce enough seed to widely scale up their use would likely cut into land used to produce cash and food crops. This is because cover crops do not generally reach a seed-producing age when planted on land between harvest and planting of food crops.

While 3-6 percent of U.S. corn farmland may not seem like much, it only takes 0.2-0.7 percent of that land to produce corn seed. Some of the cover crops that provide the greatest environmental benefits have the poorest seed production, meaning that as much as 12 percent of the U.S. corn belt would be needed to produce cover crop seed of those crops. This would be equivalent to producing 44 million metric tons less corn on those farmlands.

Invest, and look south

The authors said demand could overcome the land limitation – as long as this demand is channeled into investments in breeding programs to increase cover crop seed yield. Scientists can improve cover crops using conventional breeding techniques or biotechnological innovations, including CRISPR/Cas9 technology – essentially the same methods already used to increase seed yields in food and cash crops.

“It’s not a prohibitive investment,” said Kantar. “We need more dedicated breeding programs for cover crops.”

Alternatively, a cover crop seed industry could expand into other temperate or even tropical growing regions, giving new income opportunities to farmers who could produce seed for an emerging, global market for more sustainable crop production.

“The economic and environmental benefits of expanded cover cropping likely surpass needed investments by a very wide margin,” said Bryan Runck, the study’s lead author from the University of Minnesota.

Place a single sheet of carbon atop another at a slight angle and remarkable properties emerge, including the highly prized resistance-free flow of current known as superconductivity.

Now a team of researchers at Princeton has looked for the origins of this unusual behavior in a material known as magic-angle twisted bilayer graphene, and detected signatures of a cascade of energy transitions that could help explain how superconductivity arises in this material. The paper was published online on June 11 in the journal Nature.

"This study shows that the electrons in magic-angle graphene are in a highly correlated state even before the material becomes superconducting, "said Ali Yazdani, Class of 1909 Professor of Physics, the leader of the team that made the discovery. "The sudden shift of energies when we add or remove an electron in this experiment provides a direct measurement of the strength of the interaction between the electrons."

This is significant because these energy jumps provide a window into the collective behaviors of electrons, such as superconductivity, that emerge in magic-angle twisted bilayer graphene, a material composed of two layers of graphene in which the top sheet is rotated by a slight angle relative to the other.

In everyday metals, electrons can move freely through the material, but collisions among electrons and from the vibration of atoms give rise to resistance and the loss of some electrical energy as heat - which is why electronic devices get warm during use.

In superconducting materials, electrons cooperate. "The electrons are kind of dancing with each other," said Biao Lian, a postdoctoral research associate in the Princeton Center for Theoretical Science who will become an assistant professor of physics this fall, and one of the co-first authors of the study. "They have to collaborate to go into such a remarkable state."

By some measures, magic-angle graphene, discovered two years ago by Pablo Jarillo-Herrero and his team at the Massachusetts Institute of Technology (MIT), is one of the strongest superconductors ever discovered. Superconductivity is relatively robust in this system even though it occurs when there are very few freely moving electrons.

The researchers set out to explore how the unique crystal structure of magic-angle graphene enables collective behaviors. Electrons not only have a negative charge, but also two other characteristics: angular momentum or "spin," and possible movements in the crystal structure known as "valley" states. Combinations of spin and valley make up the various "flavors" of electrons.

The team particularly wanted to know how these flavors affect collective behaviors, so they conducted their experiments at temperatures just slightly above the point at which the electrons become strongly interacting, which the researchers likened to the parent phase of the behaviors.

"We measured the force between the electrons in the material at higher temperatures in the hopes that understanding this force will help us understand the superconductor that it becomes at lower temperatures," said Dillon Wong, a postdoctoral research fellow in the Princeton Center for Complex Materials and a co-first author.

They used a tool called a scanning tunneling microscope, in which a conductive metal tip can add or remove an electron from magic-angle graphene and detect the resulting energy state of that electron.

Because strongly interacting electrons resist the addition of a new electron, it costs some energy to add the additional electron. The researchers can measure this energy and from it determine the strength of the interaction force.

"I'm literally putting an electron in and seeing how much energy it costs to shove this electron into the cooperative bath," said Kevin Nuckolls, a graduate student in the Department of Physics, also a co-first author.

The team found that the addition of each electron caused a jump in the amount of energy needed to add another one - which would not have been the case if the electrons were able to go into the crystal and then move freely among the atoms. The resulting cascade of energy transitions resulted from an energy jump for each of the electrons' flavors - since electrons need to assume the lowest energy state possible while also not being of the same energy and same flavor as other electrons at the same location in the crystal.

A key question in the field is how the strength of interactions between electrons compares to the energy levels that the electrons would have had in the absence of such interactions. In most common and low-temperature superconductors, this is a small correction, but in rare high-temperature superconductors, the interactions among electrons are believed to change the energy levels of the electrons dramatically. Superconductivity in the presence of such a dramatic influence of interactions among electrons is very poorly understood.

The quantitative measurements of the sudden shifts detected by the researchers confirms the picture that magic-angle graphene belongs to the class of superconductors with strong interaction among the electrons.

Graphene is a single-atom-thin layer of carbon atoms, which, due to the chemical properties of carbon, arrange themselves in a flat honeycomb lattice. The researchers obtain graphene by taking a thin block of graphite - the same pure carbon used in pencils - and removing the top layer using sticky tape.

They then stack two atom-thin layers and rotate the top layer by exactly 1.1 degrees - the magic angle. Doing this causes the material to become superconducting, or attain unusual insulating or magnetic properties.

"If you're at 1.2 degrees, it's bad. It's, it's just a bland metal. There's nothing interesting happening. But if you're at 1.1 degrees, you see all this interesting behavior," Nuckolls said.

This misalignment creates an arrangement known as a moiré pattern for its resemblance to a French fabric.

To conduct the experiments, the researchers built a scanning tunneling microscope in the basement of Princeton's physics building, Jadwin Hall. So tall that it occupies two floors, the microscope sits atop a granite slab, which floats on air springs. "We need to isolate the equipment very precisely because it is extremely sensitive to vibrations," said Myungchul Oh, a postdoctoral research associate and co-first author.

Dillon Wong, Kevin Nuckolls, Myungchul Oh, and Biao Lian contributed equally to the work.

Additional contributions were made by Yonglong Xie, who earned his Ph.D. in 2019 and is now a postdoctoral researcher at Harvard University; Sangjun Jeon, who is now an assistant professor at Chung-Ang University in Seoul; Kenji Watanabe and Takashi Taniguchi of the National Institute for Material Science (NIMS) in Japan; and Princeton Professor of Physics B. Andrei Bernevig.

A similar cascade of electronic phase transitions was noted in a paper published simultaneously in Nature on June 11 by a team led by Shahal Ilani at the Weizmann Institute of Science in Israel and featuring Jarillo-Herrero and colleagues at MIT, Takashi Taniguchi and Kenji Watanabe of NIMS Japan, and researchers at the Free University of Berlin.

"The Weizmann team observed the same transitions as we did with a completely different technique," Yazdani said. "It is nice to see that their data is compatible with both our measurements and our interpretation."

Ann Arbor, June 11, 2020 - A new study in the American Journal of Preventive Medicine, published by Elsevier, takes a closer look at the benefits of volunteering to the health and well-being of volunteers, both validating and refuting findings from previous research. The results verify that adults over 50 who volunteer for at least 100 hours a year (about two hours per week) have a substantially reduced risk of mortality and developing physical limitations, higher levels of subsequent physical activity, and improved sense of well-being later on compared to individuals who do not volunteer.

"Humans are social creatures by nature. Perhaps this is why our minds and bodies are rewarded when we give to others. Our results show that volunteerism among older adults doesn't just strengthen communities, but enriches our own lives by strengthening our bonds to others, helping us feel a sense of purpose and well-being, and protecting us from feelings of loneliness, depression, and hopelessness. Regular altruistic activity reduces our risk of death even though our study didn't show any direct impact on a wide array of chronic conditions," explained lead investigator Eric S. Kim, PhD, Department of Social and Behavioral Sciences and Lee Kum Sheung Center for Health and Happiness, Harvard T.H. Chan School of Public Health, Boston; and Human Flourishing Program, Institute for Quantitative Social Science, Harvard University, Cambridge, MA, USA.

A growing body of research has linked volunteering to many health and well-being benefits, but there is still insufficient evidence to demonstrate the consistent and specific positive outcomes that are needed to develop public health interventions based on volunteerism. This large-scale study helps address this gap by evaluating 34 physical health and psychological/social well-being outcomes. This permitted direct comparisons of the potential size of effect that volunteering might have on various outcomes and also learn which outcomes volunteering does not appear to be influencing.

The study did not confirm links between volunteering and improvements to chronic conditions such as diabetes, hypertension, stroke, cancer, heart disease, lung disease, arthritis, obesity, cognitive impairment, or chronic pain.

The analysis was based on data, face-to-face interviews, and survey responses from nearly 13,000 participants randomly selected from the Health and Retirement Study (HRS), a nationally representative sample of older adults in the United States. The participants were tracked over four years in two cohorts from 2010-2016.

The growing older adult population possesses a vast array of skills and experiences that can be leveraged for the greater good of society via volunteering. While proposing further research to better understand this phenonmena, the study recommends the adoption of policies that encourage more volunteerism. Such interventions could simultaneously enhance society and foster a trajectory of healthy aging in the rapidly growing population of older adults. Further study is also needed to learn the underlying reasons for the divergence in some of the results from previous research.

A cautionary note is that these conclusions were drawn prior to the global COVID-19 pandemic, which makes social activity risky and unadvisable for the foreseeable future, However, Dr. Kim noted that "now might be a particular moment in history when society needs your service the most. If you are able to do so while abiding by health guidelines, you not only can help to heal and repair the world, but you can help yourself as well. When the COVID-19 crisis finally subsides, we have a chance to create policies and civic structures that enable more giving in society. Some cities were already pioneering this idea before the pandemic and quarantine, and I hope we have the willingness and resolve to do so in a post-COVID-19 society as well."

The amount of exchangeable potassium (K) contained in native soil does not always meet the necessary nutrient demand for a pear tree, which makes the use of K based fertilizer essential. Brazilian farmers face daily challenges to increase their productivity. Such challenges include a lack of knowledge of optimum fertilizer doses, and the critical levels of those fertilizer.

In a recent article published in Agronomy Journal, researchers report on a study to determine the impact of K based fertilizers on quality and yield of pears in an orchard with a long history of fertilizer use, in order to establish critical levels of K in the soil and leaves.

The team discovered that the levels of exchangeable K in the soil increased along with the application of K based fertilizers, but they did not find a correlation with the K concentration in leaves and fruits. Therefore, it was not possible to estimate the critical levels of K in the soil and leaves. Moreover, the fruits given higher doses of K showed the lowest values of ethylene production and respiration rate, which resulted in an increase in storage life in cold rooms and on the shelves.

In the future, camera lenses could be thousands of times thinner and significantly less resource-intensive to manufacture. Researchers from Chalmers University of Technology, Sweden, now present a new technology for making the artificial materials known as 'metasurfaces', which consist of a multitude of interacting nanoparticles that together can control light. They could have great use in the optical technology of tomorrow.

Metasurfaces can be used for optical components in portable electronics, sensors, cameras or space satellites. The Chalmers researchers' new technology for making such planar surfaces is based on a plastic that is already used today to create other microstructures.

"We put a thin layer of this plastic on a glass plate and, using a well-established technique called electron-beam lithography, we can draw detailed patterns in the plastic film, which after development will form the metasurface. The resulting device can focus light just like a normal camera lens, but it is thousands of times thinner - and can be flexible too," says Daniel Andrén, a PhD student at the Department of Physics at Chalmers and first author of the scientific article recently published in the journal ACS Photonics.

Over the past ten years, there has been a revolution in optics. The phones in our pockets have cameras comparable to a DSLR - technological masterpieces with millions of pixels of resolution. They process light with small advanced computer chips and software, and the image is recreated with the help of small coloured LEDs. These technologies have developed extremely rapidly in recent years, due mainly to smaller and more effective circuit components.

However, camera lenses themselves have not changed as much. The majority of today's lenses are based on the same physical principles, and include the same basic limitations, as the first prototypes invented in the sixteenth century. In the past decade, however, researchers have begun to work with artificial materials - metasurfaces - that could replace today's lenses.

Currently, certain issues stand in the way of large-scale manufacturing of metasurfaces. Advanced equipment is required to manufacture them, and the process is also very time-consuming. But using the Chalmers researchers' new method, the production rate can be increased several times compared to current state-of-the-art techniques. The new technology uses harmless chemicals, as well as machines that are already common in nano-manufacturing laboratories today, meaning that more researchers could now begin to study metasurfaces.

"Our method could be a step towards large-scale production of metasurfaces. That is the goal we are already working towards today. Metasurfaces can help us create different effects and offer various technological possibilities. The best is yet to come," says Ruggero Verre, a researcher at the Department of Physics at Chalmers and co-author of the scientific article.

Walking and cycling have many benefits and help reduce greenhouse gas emissions, but researchers say we need to think about what people eat to fuel their walking and cycling.

In a paper published in the international journal, Scientific Reports, the researchers say people who shift from passive modes of transport, such as driving, to active modes, such as walking, will have higher energy needs, which could lead to an increase in food-production related emissions.

The study is understood to be the first international estimate of greenhouse gas emissions associated with the extra food intake required per kilometre travelled by active transport.

Lead researcher Dr Anja Mizdrak from the University of Otago, Wellington, says producing the food required to fuel walking and cycling does come at a cost.

"We have a conundrum - but a solvable one. To maximise the benefit on greenhouse gas emissions achieved by increasing active transport, we need to also address dietary patterns. Emissions associated with active transport will be lower if walking and cycling are powered by low-carbon dietary options."

The research estimates that the additional energy expenditure required to travel one kilometre ranged from 48 to 76 kilocalories for walking and 25 to 40 kilocalories for cycling.

"If this energy is compensated with extra food intake, travelling an additional kilometre in the most economically developed countries could result in an increase in greenhouse gas emissions by 0.26 kilograms CO2-equivalents per kilometre for walking and 0.14 kilograms CO2-equivalents per kilometre for cycling."

Dr Mizdrak says there is a significant difference in greenhouse gas emissions related to food production between the most and the least economically developed nations.

"There is a wide variability in emissions required to compensate for walking and cycling between countries, representing an almost five-fold difference between the most and the least economically developed countries."

Dr Mizdrak says active transport has many advantages including more pleasant urban living, reduced air pollution, and a reduction in chronic diseases like cancer and heart disease.

"But to maximise the effect on greenhouse gas emissions achieved by increasing active transport, we need to address dietary patterns too. Emissions associated with active transport will be lower if walking and cycling are powered by low-carbon dietary options."

Dr Cristina Cleghorn, a nutrition researcher at the University of Otago, Wellington, and co-author of the research paper, says reducing meat consumption and shifting diets away from processed food and towards more vegetables, legumes, whole grains and fruits are likely to have health and environmental co-benefits.

"Given emissions associated with different food groups range widely - from 0.02 for legumes to 5.6 grams CO2-equivalents per kilocalorie for beef and lamb in one global study, consumers switching to foods with lower emissions could reduce overall dietary emissions by up to 80 per cent."

Dr Cleghorn says in high income countries, reductions in greenhouse gas emissions are largely proportional to the magnitude of meat and dairy reduction.

"In order to reduce greenhouse gas emissions we need to encourage changes in what we eat, as well as how we travel."

p>ST. LOUIS, MO, June 11, 2020 – Small RNAs are key regulators involved in plant growth and development. Two groups of small RNAs are abundant during development of pollen in the anthers – a critical process for reproductive success. A research collaboration has demonstrated the function of a genetic pathway for anther development, with this pathway proven in 2019 work to be present widely in the flowering plants that evolved over 200 million years ago. The research team was led by Blake Meyers, Ph.D., member, Donald Danforth Plant Science Center and professor, Division of Plant Sciences, University of Missouri, and Virginia Walbot, Ph.D., Professor of Biology, Stanford University. Their findings, “Dicer-like 5deficiency confers temperature-sensitive male sterility in maize” were published in the journal, Nature Communications.

Unexpectedly, their research uncovered an environmentally sensitive male sterile phenotype. By using mutants and knocking out one of the pathways, the research team produced plants that failed to make pollen, but when they lowered the temperature, they found they could recover full male fertility. This ability to turn on or turn off pollen production in different conditions could be useful for seed production. The team could also attribute the function of this pathway in anther development, an observation previously missing but important. These results are important companions to a previously published discovery, which described the evolutionary distribution of the pathway across flowering plants, “24-nt reproductive phasiRNAs are broadly present in angiosperms,” also published in the journal Nature Communications.

“Putting these two discoveries together, we can understand the role these molecules play is important for full male fertility in maize, plus, the pathway first evolved with flowering plants,” said Meyers. “Understanding the genetic mechanisms by which flowers develop is important for improving crop yields and breeding better varieties, particularly for making the high-yielding hybrid crops that support modern agriculture.”

The research team will continue to work to understand why there is an environmentally-sensitive response to changes in this pathway, and what exactly is the molecular mechanism that leads to this male sterility in the absence of this small RNA pathway. Work in a separately funded project is examining if modulation of this pathway could be used to regulate pollen development in other crops, for the improvement of seed production and crop yield.

The authors include co-first authors, Chong Teng, Ph.D., postdoctoral associate in the Meyers lab and Han Zhang, Ph.D. former postdoctoral associate in the Walbot lab. Also contributing were Kun Huang, Ph.D., postdoctoral associate in the Meyers lab, and Reza Hammond, Ph.D., former graduate student in the Meyers lab. The work is funded by the National Science Foundation.

About The Donald Danforth Plant Science Center

Founded in 1998, the Donald Danforth Plant Science Center is a not-for-profit research institute with a mission to improve the human condition through plant science. Research, education and outreach aim to have impact at the nexus of food security and the environment, and position the St. Louis region as a world center for plant science. The Center’s work is funded through competitive grants from many sources, including the National Institutes of Health, U.S. Department of Energy, National Science Foundation, and the Bill & Melinda Gates Foundation. Follow us on Twitter at @DanforthCenter.

Journal

Nature Communications

DOI

10.1038/s41467-020-16634-6