ANU researchers have found a way to improve the performance of silicon photovoltaic (PV) or solar cells. This is done through the addition of 'passivating contacts' between the metal and silicon parts of the solar cell, making it more productive.

"These findings will help push the performance of silicon solar cells closer to their theoretical limit," Mohamed Ismael, lead ANU researcher and PhD candidate said.

"Each day, the sun produces significantly more energy than needed to power the whole planet. The only limitation is our ability to economically convert it to electricity," he said.

Solar cells are devices that convert light energy in the form of photons into electrical energy. As it stands, solar cells aren't operating at their maximum capacity due to substantial electrical losses associated with the direct contact of metals with silicon.

"Transition metal oxides such as titanium oxide have many qualities that make them ideal as passivating contact layers," Dr Lachlan Black said.

"This isn't a new idea, but the way in which we combined these layers has produced better results and higher operating voltages than anything previously reported."

The research team is hoping to develop the technology to a point where it can be applied to industrial solar cells on a large scale.

The PV market is a multi-billion-dollar industry, with silicon solar cells contributing to 95 per cent of all commercial solar cells. They are predicted to remain dominant for the foreseeable future given their advantageous properties compared to competitors.

"If successful, we could see our technology in almost all new solar panels installed on your roof or utility-scale solar plants," Dr Black said.

Some practical issues still need to be addressed before the technology can be implemented, but the PV community is already working to solve these challenges.

"Improving the efficiency of solar cells guarantees more clean energy at a reduced cost. This not only helps to address climate change, but opens up new economic opportunities for this low-cost clean energy," Ismael said.Story Source:Materials provided by Australian National University. Note: Content may be edited for style and length.

Now, astronomers at the Center for Astrophysics | Harvard & Smithsonian have developed a new way to detect these elusive newborn planets -- and with it, "smoking gun" evidence of a small Neptune or Saturn-like planet lurking in a disk. The results are described today in The Astrophysical Journal Letters.

"Directly detecting young planets is very challenging and has so far only been successful in one or two cases," says Feng Long, a postdoctoral fellow at the Center for Astrophysics who led the new study. "The planets are always too faint for us to see because they're embedded in thick layers of gas and dust."

Scientists instead must hunt for clues to infer a planet is developing beneath the dust.

"In the past few years, we've seen many structures pop up on disks that we think are caused by a planet's presence, but it could be caused by something else, too" Long says. "We need new techniques to look at and support that a planet is there."

For her study, Long decided to re-examine a protoplanetary disk known as LkCa 15. Located 518 light years away, the disk sits in the Taurus constellation on the sky. Scientists previously reported evidence for planet formation in the disk using observations with the ALMA Observatory.

Long dove into new high-resolution ALMA data on LkCa 15, obtained primarily in 2019, and discovered two faint features that had not previously been detected.

About 42 astronomical units out from the star -- or 42 times the distance Earth is from the Sun -- Long discovered a dusty ring with two separate and bright bunches of material orbiting within it. The material took the shape of a small clump and a larger arc, and were separated by 120 degrees.

Long examined the scenario with computer models to figure out what was causing the buildup of material and learned that their size and locations matched the model for the presence of a planet.

"This arc and clump are separated by about 120 degrees," she says. "That degree of separation doesn't just happen -- it's important mathematically."

Long points to positions in space known as Lagrange points, where two bodies in motion -- such as a star and orbiting planet -- produce enhanced regions of attraction around them where matter may accumulate.

"We're seeing that this material is not just floating around freely, it's stable and has a preference where it wants to be located based on physics and the objects involved," Long explains.

In this case, the arc and clump of material Long detected are located at the L4 and L5 Lagrange points. Hidden 60 degrees between them is a small planet causing the accumulation of dust at points L4 and L5.

The results show the planet is roughly the size of Neptune or Saturn, and around one to three million years old. (That's relatively young when it comes to planets.)

Directly imaging the small, newborn planet may not be possible any time soon due to technology constraints, but Long believes further ALMA observations of LkCa 15 can provide additional evidence supporting her planetary discovery.

She also hopes her new approach for detecting planets -- with material preferentially accumulating at Lagrange points -- will be utilized in the future by astronomers.

"I do hope this method can be widely adopted in the future," she says. "The only caveat is that this requires very deep data as the signal is weak."

Long recently completed her postdoctoral fellowship at the Center for Astrophysics and will join the University of Arizona as a NASA Hubble Fellow this September.

Co-authors on the study are Sean Andrews, Chunhua Qi, David Wilner and Karin Oberg of the CfA; Shangjia Zhang and Zhaohuan Zhu of the University of Nevada; Myriam Benisty of the University of Grenoble; Stefano Facchini of the University of Milan; Andrea Isella of Rice University; Jaehan Bae of the University of Florida; Jane Huang of the University of Michigan and Ryan Loomis of the National Radio Astronomy Observatory.

The team used high resolution ALMA observations taken with Band 6 (1.3mm) and Band 7 (0.88mm) receivers.

COPD is a long-term condition linked to reduced lung function that causes inflammation in the lungs and a narrowing of the airways, making breathing difficult. According to the Global Burden of Disease (GBD) project COPD is the third leading cause of death worldwide, and the number of global COPD deaths are expected to increase over the next ten years.

Lung function normally declines as we age, but the new research published today (9 July, 2019) in the European Respiratory Journal [1] suggests that air pollution may contribute to the ageing process and adds to the evidence that breathing in polluted air harms the lungs.

Anna Hansell is Professor of Environmental Epidemiology in the Centre for Environmental Health and Sustainability at the University of Leicester, UK, and was part of the research team. She said: "There are surprisingly few studies that look at how air pollution affects lung health. To try and address this, we assessed more than 300,000 people using data from the UK Biobank study to examine whether air pollution exposure was linked to changes in lung function, and whether it affected participants' risk of developing COPD."

The researchers used a validated air pollution model to estimate the levels of pollution that people were exposed to at their homes when they enrolled in the UK Biobank study. The types of pollutants the researchers investigated included particulate matter (PM10), fine particulate matter (PM2.5) and nitrogen dioxide (NO2), which are produced by burning fossil fuels from car and other vehicle exhausts, power plants and industrial emissions.

Participants answered detailed health questionnaires as part of the UK Biobank data collection, and lung function was measured using spirometry tests performed by medical professionals at Biobank assessment centers at enrolment between 2006 and 2010. Spirometry is a simple test used to help diagnose and monitor certain lung conditions by measuring how much air can be breathed out in one forced breath.

The research team then conducted multiple tests to see how long-term exposure to higher levels of the different air pollutants was linked to changes to participants' lung function. The participants' age, sex, body mass index (BMI), household income, education level, smoking status, and exposure to secondhand smoke were accounted for in the analyses. Further analyses also looked at whether working in occupations that increase the risk of developing COPD impacted disease prevalence.

The data showed that for each annual average increase of five micrograms per cubic meter of PM2.5 in the air that participants were exposed to at home, the associated reduction in lung function was similar to the effects of two years of ageing.

When the researchers assessed COPD prevalence, they found that among participants living in areas with PM2.5 concentrations above World Health Organization (WHO) annual average guidelines of ten micrograms per cubic meter (10 μg/m3), COPD prevalence was four times higher than among people who were exposed to passive smoking at home, and prevalence was half that of people who have ever been a smoker.

The current EU air quality limits for PM2.5 is 25 micrograms per cubic meter (25 μg/m3), which is higher than the levels that the researchers noted as being linked to reduced lung function.

Professor Hansell explained: "In one of the largest analyses to date, we found that outdoor air pollution exposure is directly linked to lower lung function and increased COPD prevalence. We found that people exposed to higher levels of pollutants had lower lung function equivalent to at least a year of ageing.

"Worryingly, we found that air pollution had much larger effects on people from lower income households. Air pollution had approximately twice the impact on lung function decline and three times the increased COPD risk on lower-income participants compared to higher-income participants who had the same air pollution exposure.

"We accounted for participants' smoking status and if their occupation might affect lung health, and think this disparity could be related to poorer housing conditions or diet, worse access to healthcare or long-term effects of poverty affecting lung growth in childhood. However, further research is needed to investigate the differences in effects between people from lower- and higher-income homes."

The researchers were not able to track participants' exposure to pollutants in their daily lives, and say that study participants were generally wealthier and healthier than the wider general public, which could have resulted in underestimations of the strength of the links between declining lung function and air pollution exposure.

Professor Tobias Welte from Hannover University, Germany, is President of the European Respiratory Society and was not involved in the study. He said: "The findings of this large study reinforce that exposure to polluted air seriously harms human health by reducing life expectancy and making people more prone to developing chronic lung disease.

"Access to clean air is a fundamental need and right for all citizens in Europe. Governments have a responsibility to protect this right by ensuring that maximum pollutant levels indicated by the World Health Organization are not breached across our cities and towns. Breathing is the most basic human function required to sustain life, which is why we must continue to fight for the right to breathe clean air."

The research team are conducting further studies to look at whether genetic factors interact with air pollution and its effects on health.

The researchers synthesized results from more than a dozen studies with rodent, monkey, and human brain imaging, and used it to propose a new computational model that explains how our breathing influences the brain's expectations.

"What we found is that, across many different types of tasks and animals, brain rhythms are closely tied to the rhythm of our breath. We are more sensitive to the outside world when we are breathing in, whereas the brain tunes out more when we breathe out. This also aligns with how some extreme sports use breathing, for example professional marksmen are trained to pull the trigger at the end of exhalation," explains Professor Micah Allen.

The study suggest that breathing is more than just something we do to stay alive, explains Micah Allen.

"It suggests that the brain and breathing are closely intertwined in a way that goes far beyond survival, to actually impact our emotions, our attention, and how we process the outside world. Our model suggests there is a common mechanism in the brain which links the rhythm of breathing to these events."

Breathing can affect our mental health

Understanding how breathing shapes our brain, and by extension, our mood, thoughts, and behaviours, is an important goal in order to better prevent and treat mental illness.

"Difficulty breathing is associated with a very large increase in the risk for mood disorders such as anxiety and depression. We know that respiration, respiratory illness, and psychiatric disorders are closely linked. Our study raises the possibility that the next treatments for these disorders might be found in the development of new ways to realign the rhythms of the brain and body, rather than treating either in isolation," explains Micah Allen.

Stabilising our mind through breathing is a well-known and used tactic in many traditions such as yoga and meditation. The new study sheds light on how the brain makes it possible. It suggests that there are three pathways in the brain that control this interaction between breathing and brain activity. It also suggests that our pattern of breathing makes the brain more "excitable," meaning neurons are more likely to fire during certain times of breathing

New research to come

The new study gives researchers a new target for future studies in for example persons with respiratory or mood disorders, and Micah Allen and his group already have already started new projects based on the study.

"We have a variety of ongoing projects that are both building on and testing various parts of the model we have proposed. PhD. Student Malthe Brændholt is conducting innovative brain imaging studies in humans, to try and understand how different kinds of emotional and visual perception are influenced by breathing in the brain," says Micah Allen.

The team is also collaborating with the Pulmonology team at Aarhus University Hospital, where tools developed in the lab are used to understand whether person suffering from long-covid may have disruptions in the breath-brain alignment. And there are more projects coming, says Micah Allen.

"We will be using a combination of human and animal neuroimaging to better understand how breathing influences the brain, and also utilising exploring how different drugs influence respiratory-brain interaction. We would also like to some day study how lifestyle factors like stress, sleep, and even things like winter swimming influence breath-brain interaction. We are very excited to continue this research," says Micah Allen.Story Source:Materials provided by Aarhus University. Original written by Vibe Bregendahl Noordeloos. Note: Content may be edited for style and length.

In a study that could help to understand the evolutional origin of sleep in animals, an international team of researchers has shown that tiny, water-dwelling hydras not only show signs of a sleep-like state despite lacking central nervous systems but also respond to molecules associated with sleep in more evolved animals.

"We now have strong evidence that animals must have acquired the need to sleep before acquiring a brain," says Taichi Q. Itoh, assistant professor at Kyushu University's Faculty of Arts and Science and leader of the research reported in Science Advances.

While sleeping behavior was also recently found in jellyfish, a relative of hydras and fellow member of the phylum Cnidaria, the new study from researchers at Kyushu University in Japan and Ulsan National Institute of Science and Technology in Korea found that several chemicals eliciting drowsiness and sleep even in humans had similar effects on the species Hydra vulgaris.

"Based on our findings and previous reports regarding jellyfish, we can say that sleep evolution is independent of brain evolution," states Itoh.

"Many questions still remain regarding how sleep emerged in animals, but hydras provide an easy-to-handle creature for further investigating the detailed mechanisms producing sleep in brainless animals to help possibly one day answer these questions."

Only a couple of centimeters long, hydras have a diffuse network of nerves but lack the centralization associated with a brain.

While sleep is often monitored based on the measurement of brain waves, this is not an option for tiny, brainless animals.

As an alternative, the researchers used a video system to track movement to determine when hydras were in a sleep-like state characterized by reduced movement -- which could be disrupted with a flash of light.

Instead of repeating every 24 hours like a circadian rhythm, the researchers found that the hydras exhibit a four-hour cycle of active and sleep-like states.

More importantly, the researchers uncovered many similarities related to sleep regulation on a molecular and genetic level regardless of the possession of a brain.

Exposing the hydras to melatonin, a commonly used sleep aid, moderately increased the sleep amount and frequency, while the inhibitory neurotransmitter GABA, another chemical linked to sleep activity in many animals, greatly increased sleep activity.

On the other hand, dopamine, which causes arousal in many animals, actually promoted sleep in the hydras.

"While some sleep mechanisms appear to have been conserved, others may have switched function during evolution of the brain," suggests Itoh.

Furthermore, the researchers could use vibrations and temperature changes to disturb the hydras' sleep and induce signs of sleep deprivation, causing the hydras to sleep longer during the following day and even suppressing cell proliferation.

Investigating more closely, the researchers found that sleep deprivation led to changes in the expression of 212 genes, including one related to PRKG, a protein involved in sleep regulation in the wide range of animals, including mice, fruit flies, and nematodes.

Disrupting other fruit fly genes appearing to share a common evolutional origin with the sleep-related ones in hydras altered sleep duration in fruit flies, and further investigation of such genes may help to identify currently unknown sleep-related genes in animals with brains.

"Taken all together, these experiments provide strong evidence that animals acquired sleep-related mechanisms before the evolutional development of the central nervous system and that many of these mechanisms were conserved as brains evolved," says Itoh.

story Source:Materials provided by Kyushu University. Note: Content may be edited for style and length.

"I'm trained as a drummer, and most of my research career has been focused on the rhythmic aspects of music and how they make us move," says first author Daniel Cameron, a neuroscientist from McMaster University. "Music is a biological curiosity -- it doesn't reproduce us, it doesn't feed us, and it doesn't shelter us, so why do humans like it and why do they like to move to it?"

Cameron conducts research at the McMaster LIVELab, which connects science with live performance in a unique research theater. It is equipped with 3D motion capture, a Meyer sound system that can replicate various concert environments, and enhanced speakers that can produce extremely low frequencies, so low they were undetectable to the human ear.

For the Current Biology study, Cameron and colleagues recruited participants attending a LIVELab concert for electronic musical duo Orphx. The concertgoers were equipped with motion-sensing headbands to monitor their dance moves. Additionally, they were asked to fill out survey forms before and after the event. These forms were used to ensure the sound was undetectable, measure concert enjoyment, and examine how the music felt physically.

Throughout the 45-minute concert, the researchers manipulated the very-low bass-playing speakers, turning them on and off every two minutes. They found the amount of movement was 12 percent greater when the speakers were on.

"The musicians were enthusiastic to participate because of their interest in this idea that bass can change how the music is experienced in a way that impacts movement," says Cameron. "The study had high ecological validity, as this was a real musical and dance experience for people at a real live show."

The feeling of vibration through touch and the interactions between the inner ear and the brain have close links to the motor system. The researchers speculate these physical processes are at work in the neurological connection between music and movement. This anatomy can pick up on low frequencies and can affect the perception of "groove," spontaneous movement, and rhythm perception.

"Very low frequencies may also affect vestibular sensitivity, adding to people's experience of movement. Nailing down the brain mechanisms involved will require looking the effects of low frequencies on the vestibular, tactile, and auditory pathways," says Cameron.

Story Source:Materials provided by Cell Press. Note: Content may be edited for style and length.

Modern computer processors contain many computing units, called cores, which share the same hardware resources. The on-chip interconnect is the component that enables these cores to communicate with each other. But when programs on multiple cores run simultaneously, there is a chance they can delay one another when they use the interconnect to send data across the chip at the same time.

By monitoring and measuring these delays, a malicious agent could conduct what is known as a "side-channel attack" and reconstruct secret information that is stored in a program, such as a cryptographic key or password.

MIT researchers reverse-engineered the on-chip interconnect to study how this kind of attack would be possible. Drawing on their discoveries, they built an analytical model of how traffic flows between the cores on a processor, which they used to design and launch surprisingly effective side-channel attacks. Then they developed two mitigation strategies that enable a user to improve security without making any physical changes to the computer chip.

"A lot of current side-channel defenses are ad hoc -- we see a little bit of leakage here and we patch it. We hope our approach with this analytical model pushes more systematic and robust defenses that eliminate whole classes of attacks at the same time," says co-lead author Miles Dai, MEng '21.

Dai wrote the paper with co-lead author Riccardo Paccagnella, a graduate student at the University of Illinois at Urbana-Champaign; Miguel Gomez-Garcia '22; John McCalpin, a research scientist at Texas Advanced Computing Center; and senior author Mengjia Yan, the Homer A. Burnell Career Development Assistant Professor of Electrical Engineering and Computer Science (EECS) and a member of the Computer Science and Artificial Intelligence Laboratory (CSAIL). The research is being presented at the USENIX Security Conference.

Probing processors

A modern processor is like a two-dimensional grid, with multiple cores laid out in rows and columns. Each core has its own cache where data are stored, and there is also a larger cache that is shared across the entire processor. When a program located on one core needs to access data in a cache that is on another core or in the shared cache, it must use the on-chip interconnect to send this request and retrieve the data.

Though it is a large component of the processor, the on-chip interconnect remains understudied because it is difficult to attack, Dai explains. A hacker needs to launch the attack when traffic from two cores is actually interfering with each other, but since traffic spends so little time in the interconnect, it is difficult to time the attack just right. The interconnect is also complex, and there are multiple paths traffic can take between cores.

To study how traffic flows on the interconnect, the MIT researchers created programs that would intentionally access memory caches located outside their local cores.

"By testing out different situations, trying different placements, and swapping out locations of these programs on the processor, we can understand what the rules are behind traffic flows on the interconnect," Dai says.

They discovered that the interconnect is like a highway, with multiple lanes going in every direction. When two traffic flows collide, the interconnect uses a priority arbitration policy to decide which traffic flow gets to go first. More "important" requests take precedence, like those from programs that are critical to a computer's operations.

Using this information, the researchers built an analytical model of the processor that summarizes how traffic can flow on the interconnect. The model shows which cores would be most vulnerable to a side-channel attack. A core would be more vulnerable if it can be accessed through many different lanes. An attacker could use this information to select the best core to monitor to steal information from a victim program.

"If the attacker understands how the interconnect works, they can set themselves up so the execution of some sensitive code would be observable through interconnect contention. Then they can extract, bit by bit, some secret information, like a cryptographic key," Paccagnella explains.

Effective attacks

When the researchers used this model to launch side-channel attacks, they were surprised by how quickly the attacks worked. They were able to recover full cryptographic keys from two different victim programs.

After studying these attacks, they used their analytical model to design two mitigation mechanisms.

In the first strategy, the system administrator would use the model to identify which cores are most vulnerable to attacks and then schedule sensitive software to run on less vulnerable cores. For the second mitigation strategy, the administrator could reserve cores located around a susceptible program and run only trusted software on those cores.

The researchers found that both mitigation strategies were able to significantly reduce the accuracy of side-channel attacks. Neither requires the user to make any changes to the physical hardware, so the mitigations would be relatively easy to implement, Dai says.

Ultimately, they hope their work inspires more researchers to study the security of on-chip interconnects, Paccagnella says.

"We hope this work highlights how the on-chip interconnect, which is such a large component of computer processors, remains an overlooked attack surface. In the future, as we build systems that have stronger isolation properties, we should not ignore the interconnect," he adds.

This work was funded, in part, by the National Science Foundation and the Air Force Office of Scientific Research.

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Materials provided by Massachusetts Institute of Technology. Original written by Adam Zewe. Note: Content may be edited for style and length.

Materials with strong electronic interactions can have applications in energy-efficient electronics. When these materials are placed on a substrate, their electronic properties are changed by charge transfer, strain, and hybridisation.

The study also shows that electric fields and applied strain could be used to 'switch' interacting phases such as magnetism on and off, allowing potential applications in future energy-efficient electronics.

TURNING MAGNETISM ON AND OFF WITH SUBSTRATES

Strong interactions between electrons in materials gives rise to effects such as magnetism and superconductivity. These effects have uses in magnetic memory, spintronics, and quantum computing, making them appealing for emerging technologies.

Last year, another study at Monash discovered strong electronic interactions in a 2D metal-organic framework. The researchers found signatures of magnetism in this material. They showed that this magnetism arose due to strong interactions that were only present when the non-magnetic components were brought together.

This material was grown on a metallic substrate. The substrate was important for the growth and measurement of the material.

Explainer: Metal-organic framework

A crystalline material where organic molecules are connected by metal atoms. Metal-organic frameworks can show many different properties by changing the molecules or metal atoms. Understanding quasiparticle excitations and their interactions is crucial for efforts to control complex materials (such as high-temperature superconductors and topological insulators) that may form the basis of future low-energy electronics and quantum information processing.

"We observed this effect when the material was grown on silver, but not when it was grown on copper, despite them being very similar," says Bernard Field (Monash), co-author of the earlier study and lead author of the current study.

"So that begged the question: Why did the material behave so differently on different substrates?"

The researchers simulated the metal-organic framework on many different substrates to determine under what conditions magnetism could emerge.

They also created a simple model which accurately described the physical phenomena in their atomic-scale simulations. This model allowed the team to quickly and easily explore a wider range of systems with fine control over the important parameters.

Three key variables were found to determine the effect of substrates on electronic interactions: charge transfer, strain, and substrate hybridisation.

• Charge transfer is when a substrate gives or takes electrons from the 2D material. The effect of interactions was strongest when the material had one free electron per molecule.
• Strain is when a substrate stretches or squeezes the 2D material. When the material is stretched, electrons have difficulty moving between molecules and atoms, so they experience local interactions more strongly.
• Hybridisation is when the electronic character of the substrate and the 2D material are mixed due to coupling between them. Metallic substrates often have strong hybridisation, which can suppress magnetism. But insulating substrates, such as atomically-thin hexagonal boron nitride, have very weak hybridisation and preserve the electronic interactions in the material.

With this understanding of what the key variables are, it is possible to consider how to manipulate these variables to control the electronic interactions.

The study showed that an electric field could turn magnetism on and off by changing the charge transfer.

Electric fields are how existing transistors operate. Having electric control of magnetic phases is vital for using these materials in electronic devices.

The study also showed that applied strain could turn magnetism on and off. This could be achieved using piezoelectric materials. It is also an important consideration for flexible electronics.

"The team is continuing to investigate strong interactions in 2D metal-organic frameworks, which provide a rich platform to explore novel quantum physics applied for energy-efficient electronic devices," says corresponding author Prof Nikhil Medhekar (Monash Department of Materials Science and Engineering), who led the study, "We are investigating more advanced methods for simulating strong interactions between electrons."

"This work provides quantitative predictions, using diverse theoretical formalisms, on the electronic properties of low-dimensional nanomaterials on a wide range of substrates and conditions," says co-author A/Prof Agustin Schiffrin (Monash School of Physics and Astronomy), who leads experimental research on these materials, "This can guide future real-world experiments, which is extremely valuable for experimental researchers."

This study was supported through the Australian Research Council (Centre of Excellence and Future Fellowship programs). Resources for numerical calculations were provided by the National Computing Infrastructure (NCI) and Pawsey Supercomputing Centre.

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Materials provided by ARC Centre of Excellence in Future Low-Energy Electronics Technologies. Note: Content may be edited for style and length.