“A large amount of heat from the energy we consume is essentially being thrown away, often dispersed right into the atmosphere,” said Shashank Priya, associate vice president for research and professor of materials science and engineering at Penn State. “We haven’t had cost-effective ways with conformal shapes to trap and convert that heat to useable energy. This research opens that door.”

Penn State researchers have been working to improve the performance of thermoelectric generators — devices that can convert differences in temperature to electricity. When the devices are placed near a heat source, electrons moving from the hot side to the cold side produce an electric current, the scientists said.

In prior work, the team created rigid devices that were more efficient than commercial units in high-temperature applications. Now the team has developed a new manufacturing process to produce flexible devices that offer higher power output and efficiency, the scientists said.

“These results provide a promising pathway toward widespread utilization of thermoelectric technology into waste heat recovery application,” said Wenjie Li, assistant research professor at Penn State. “This could have a significant impact on the development of practical thermal to electrical generators.”

Flexible devices better fit the most attractive waste heat sources, like pipes in industrial and residential buildings and on vehicles, the scientists said. And they don’t have to be glued on surfaces like traditional, rigid devices, which further decreases efficiency.

In tests being conducted on a gas flue, the new device exhibited 150% higher power density than other state-of-the-art units, the scientists reported in Applied Materials & Interfaces. A scaled-up version, just over 3-inches squared, maintained a 115% power density advantage. That version exhibited a total power output of 56.6 watts when placed on the hot surface, the scientists said.

“Think about an industrial power plant with pipes hundreds of feet long,” Priya said. “If you can wrap these devices around an area that large, you could generate kilowatts of energy from wasted heat that’s normally just being thrown away. You could convert discarded heat into something useful.”

Thermoelectric devices are made up of small couples, each resembling a table with two legs. Many of these two-leg couples are connected together, typically forming a flat, square device.

In creating the new device, scientists placed six couples along a thin strip. They then used flexible metal foil to connect 12 of the strips together, creating a device with 72 couples. Liquid metal was used between the layers of each strip to improve device performance, the scientist said.

“As you scale up these devices, you often lose power density, making it challenging to fabricate large-scale thermoelectric generators,” said Bed Poudel, associate research professor at Penn State. “This illustrates the extraordinary performance of our 72-couple device.”

The 72-couple device exhibited the highest reported output power and device power density from a single thermoelectric generator, the scientists said.

The gaps between the strips provide the flexibility to fit around shapes like pipes. The gaps also allow for flexibility in altering the fill factor, or the ratio between the area of thermoelectric material and the area of the device, which can be used to optimize thermoelectric devices for different heat sources, the scientists said.

Other Penn State researchers on the project were Amin Nozariasbmarz, assistant research professor; Han Byul Kang and Hangtain Zhu, postdoctoral researchers; and Carter Dettor, a former graduate student.

Ravi Anant Kishore, research engineer at National Renewable Energy Laboratory, also contributed.

Various authors contributing to this study were supported through Department of Energy, Office of Naval Research, Army Research Office, National Science Foundation and Defense Advanced Research Projects Agency.

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Materials provided by Penn State. Original written by Matthew Carroll. Note: Content may be edited for style and length.

Water can exist in three phases: a frozen solid, a liquid, and a gas. When heat is applied to a frozen solid, it becomes a liquid. When applied to the liquid, it becomes vapor. This elementary principle is familiar to anyone who has observed a glass of iced tea on a hot day, or boiled a pot of water to make spaghetti.

When the heat source is hot enough, the water’s behavior changes dramatically. According to Boreyko, a water droplet deposited onto an aluminum plate heated to 150 degrees Celsius (302 degrees Fahrenheit) or above will no longer boil. Instead, the vapor that forms when the droplet approaches the surface will become trapped beneath the droplet, creating a cushion that prevents the liquid from making direct contact with the surface. The trapped vapor causes the liquid to levitate, sliding around the heated surface like an air hockey puck. This phenomenon is known as the Leidenfrost effect, named for the German doctor and theologian who first described it in a 1751 publication.

This commonly accepted scientific principle applies to water as a liquid, floating on a bed of vapor. Boreyko’s team found themselves wondering: Could ice perform in the same way?

“There are so many papers out there about levitating liquid, we wanted to ask the question about levitating ice,” said Boreyko. “It started as a curiosity project. What drove our research was the question of whether or not it was possible to have a three-phase Leidenfrost effect with solid, liquid, and vapor.”

Going into the ice

Curiosity sparked the first investigation in Boreyko’s lab some five years ago in the form of a research project by then-undergraduate student Daniel Cusumano. What he observed was fascinating. Even when the aluminum was heated above 150 C, the ice did not levitate on vapor as liquid does. Cusumano continued raising the temperature, observing the behavior of the ice as the heat increased. What he found was that the threshold for levitation was dramatically higher: 550 C (1022 F) rather than 150 C. Up until that threshold, the meltwater beneath the ice continued to boil in direct contact with the surface, rather than exhibit the Leidenfrost effect.

What was going on underneath the ice that prolonged the boiling? The project was picked back up by graduate student Mojtaba Edalatpour a short time later, to solve the mystery. Edalatpour had been working with Boreyko to develop novel methods of heat transfer and put that knowledge to work in approaching this problem. The answer turned out to be the temperature differential in the meltwater layer beneath the ice. The meltwater layer has two different extremes: Its bottom is boiling, which fixes the temperature at about 100 C, but its top is adhered to the remaining ice, which fixes it at about 0 C. Edalatpour’s model revealed that the maintenance of this extreme temperature differential consumes most of the surface’s heat, explaining why levitation was more difficult for ice.

Boreyko elaborated. “The temperature differential the ice is uniquely creating across the water layer has changed what happens in the water itself, because now most of the heat from the hot plate has to go across the water to maintain that extreme differential. So only a tiny fraction of the energy can be used to produce vapor anymore.”

The elevated temperature of 550 degrees Celsius for the icy Leidenfrost effect is practically important. Boiling water is optimally transporting heat away from the substrate, which is why you feel ample heat rising from a pot of water that is boiling, but not from a pot of water that is merely hot. This means that the difficulty in levitating ice is actually a good thing, as the larger temperature window for boiling will result in better heat transfer compared to using a liquid alone.

“It is much harder to levitate the ice than it was to levitate the water droplet,” said Boreyko. “Heat transfer plummets as soon as levitation begins, because when liquid levitates, it doesn’t boil anymore. It’s floating over the surface rather than touching, and touching is what causes it to boil the heat away. So, for heat transfer, levitation is terrible. Boiling is incredible.”

Using ice for heat transfer

As the team explored possibilities for practical application, they looked to their existing work. Since Edalatpour had extensive research in heat transfer, that topic became a logical fit.

Heat transfer comes most into play for cooling off things like computer servers or car engines. It requires a substance or mechanism that can move energy away from a hot surface, redistributing heat quickly to reduce the wear and tear on metal parts. In nuclear power plants, the application of ice to induce rapid cooling could become an easily-deployed emergency measure if power fails, or a regular practice for servicing power plant parts.

There are also potential applications for metallurgy. To produce alloys, it is necessary to quench the heat from metals that have been shaped in a narrow window of time, making the metal stronger and less brittle. If ice were applied, it would allow heat to be offloaded rapidly through the three water phases, quickly cooling the metal.

Boreyko also foresees a potential for applications in firefighting.

“You could imagine having a specially made hose that is spraying ice chips as opposed to a jet of water,” he said. “This is not science fiction. I visited an aerospace company that has an icing tunnel and they already have this technology where a nozzle sprays out ice particles as opposed to water droplets.”

With myriad possibilities, Boreyko and Edalatpour are excited about the new contribution that has come to the science world. Looking back over the past five years, they still credit this exciting development to their shared spark of curiosity and the drive to be creative in research.

Unlike a conventional camera, the light-field camera contains micro-lens arrays in front of the image sensor, which makes the camera small enough to fit into a smart phone, while allowing it to acquire the spatial and directional information of the light with a single shot. The technique has received attention as it can reconstruct images in a variety of ways including multi-views, refocusing, and 3D image acquisition, giving rise to many potential applications.

However, the optical crosstalk between shadows caused by external light sources in the environment and the micro-lens has limited existing light-field cameras from being able to provide accurate image contrast and 3D reconstruction.

The joint research team applied a vertical-cavity surface-emitting laser (VCSEL) in the near-IR range to stabilize the accuracy of 3D image reconstruction that previously depended on environmental light. When an external light source is shone on a face at 0-, 30-, and 60-degree angles, the light field camera reduces 54% of image reconstruction errors. Additionally, by inserting a light-absorbing layer for visible and near-IR wavelengths between the micro-lens arrays, the team could minimize optical crosstalk while increasing the image contrast by 2.1 times.

Through this technique, the team could overcome the limitations of existing light-field cameras and was able to develop their NIR-based light-field camera (NIR-LFC), optimized for the 3D image reconstruction of facial expressions. Using the NIR-LFC, the team acquired high-quality 3D reconstruction images of facial expressions expressing various emotions regardless of the lighting conditions of the surrounding environment.

The facial expressions in the acquired 3D images were distinguished through machine learning with an average of 85% accuracy — a statistically significant figure compared to when 2D images were used. Furthermore, by calculating the interdependency of distance information that varies with facial expression in 3D images, the team could identify the information a light-field camera utilizes to distinguish human expressions.

Professor Ki-Hun Jeong said, “The sub-miniature light-field camera developed by the research team has the potential to become the new platform to quantitatively analyze the facial expressions and emotions of humans.” To highlight the significance of this research, he added, “It could be applied in various fields including mobile healthcare, field diagnosis, social cognition, and human-machine interactions.”

This research was published in Advanced Intelligent Systems online on December 16, under the title, “Machine-Learned Light-field Camera that Reads Facial Expression from High-Contrast and Illumination Invariant 3D Facial Images.” This research was funded by the Ministry of Science and ICT and the Ministry of Trade, Industry and Energy.

The study, published in Earth and Planetary Science Letters, analysed the formation of more than 500 large Martian craters using a crater detection algorithm previously developed at Curtin, which automatically counts the visible impact craters from a high-resolution image.

Despite previous studies suggesting spikes in the frequency of asteroid collisions, lead researcher Dr Anthony Lagain, from Curtin’s School of Earth and Planetary Sciences, said his research had found they did not vary much at all for many millions of years.

Dr Lagain said counting impact craters on a planetary surface was the only way to accurately date geological events, such as canyons, rivers and volcanoes, and to predict when, and how big, future collisions would be.

“On Earth, the erosion of plate tectonics erases the history of our planet. Studying planetary bodies of our Solar System that still conserve their early geological history, such as Mars, helps us to understand the evolution of our planet,” Dr Lagain said.

“The crater detection algorithm provides us with a thorough understanding of the formation of impact craters including their size and quantity, and the timing and frequency of the asteroid collisions that made them.”

Past studies had suggested that there was a spike in the timing and frequency of asteroid collisions due to the production of debris, Dr Lagain said.

“When big bodies smash into each other, they break into pieces or debris, which is thought to have an effect on the creation of impact craters,” Dr Lagain said.

“Our study shows it is unlikely that debris resulted in any changes to the formation of impact craters on planetary surfaces.”

Co-author and leader of the team that created the algorithm, Professor Gretchen Benedix, said the algorithm could also be adapted to work on other planetary surfaces, including the Moon.

“The formation of thousands of lunar craters can now be dated automatically, and their formation frequency analysed at a higher resolution to investigate their evolution,” Professor Benedix said.

“This will provide us with valuable information that could have future practical applications in nature preservation and agriculture, such as the detection of bushfires and classifying land use.”

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Materials provided by Curtin University. Note: Content may be edited for style and length.

Studies since the start of the pandemic have noted that pigs can be infected by the virus if exposed to high doses, but the infection is self-limited and pigs don’t show clinical signs of disease nor do they transmit the virus to other animals. So Rahul Nelli, a research assistant professor of veterinary diagnostic and production animal medicine, and Luis Gimenez-Lirola, an associate professor of veterinary diagnostic and production animal medicine, set out to find out why in a newly published study in the academic journal Cell Death Discovery. What they found could lead to new ways to treat humans who contract COVID-19, the disease that results from infection by the virus SARS-CoV-2, said Nelli and Gimenez-Lirola.

Nelli and Gimenez-Lirola have studied how coronaviruses affect pigs for years. They’ve developed models that allow them to study in detail how viruses infect pigs and pig cells and how the cells respond to fight the infection. For the latest experiments, they introduced the virus to cultured porcine and human respiratory epithelial cells, which line most of the respiratory tract. They found the pig cells underwent apoptosis, or controlled cell death, in response to infection at a higher rate than human epithelial cells.

“When we looked under the microscope there was an interesting phenomenon going on inside the cells,” Nelli said. “The nuclei of the infected pig cells were starting to shred into fragments but not uninfected pig cells.”

That shredding of the nucleus is a telltale sign of apoptosis, which may be a key in helping pigs avoid symptoms after exposure to SARS-CoV-2. Triggering apoptosis early in the infection essentially causes minimal tissue damage and confines viral replication, thus limiting severe illness. Human cells can undergo apoptosis in response to coronavirus infection as well, but the study found human cells do so much less frequently than porcine cells. Pig cells are roughly 100 times more likely to undergo apoptosis than human cells, according to the study.

Human cells are more likely to go through necrosis, another form of cell death that’s less controlled than apoptosis. During necrosis, the contents of a cell release into the surrounding space, provoking a strong hyperimmune response that isn’t triggered during apoptosis.

The researchers surmise that a wide-scale apoptosis response is helpful for avoiding disease because it disposes of infected cells quickly without the immune system overreacting, while wide-scale necrosis and the resulting hyperimmune response is less favorable to host cells.

“We don’t want to over-conclude, but this response is probably something intrinsic to the pig immune system that is innate and not acquired,” Giminez-Lirola said. “The idea is to kill the virus subtly but fast enough so there’s not an excessive immune response triggered.”

The researchers said further study could lead to therapies designed to trigger apoptosis in human cells, allowing people infected with the coronavirus to avoid severe symptoms.

The next step for the ISU research team is to identify all the genes activated during the infectious process and compare them with other animal species in which those genes are present. That could give them further clues about how and why other animals, such as deer, can carry the virus without suffering symptoms of disease.

In addition to Nelli and Gimenez-Lirola, the research team included Kruttika Phadke, Gino Castillo, Lu Yen and Bryan Bellaire at Iowa State. Amy Saunders, Rolf Rauh and William Nelson of Maryland-based Tetracore, Inc., are also listed as co-authors of the study.

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Materials provided by Iowa State University. Note: Content may be edited for style and length.

“It is important for patients with cancer who are receiving chemotherapy to receive a COVID-19 vaccine,” says Saranya Chumsri, M.D., a Mayo Clinic hematologist and oncologist, and author of the paper. Dr. Chumsri says this advice also applies to patients with cancer who are taking a CDK 4/6 inhibitors. These inhibitors are a newer class of medicines used to treat hormone-receptor-positive and HER2-negative breast cancers.

Dr. Chumsri says that while CDK 4/6 inhibitors are not conventionally considered to be as immunosuppressive as chemotherapy, her research on patients with breast cancer who take these drugs found that they exhibited less optimal neutralizing antibody activity. Dr. Chumsri recommends that antibody levels be tested in these patients after vaccination, and they should consider receiving booster vaccinations for COVID-19.

Dr. Chumsri anticipates having additional data later this year regarding broader immune responses to COVID-19 vaccinations, including cellular and antibody responses in patients receiving chemotherapy and targeted therapies with booster vaccinations.

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Materials provided by Mayo Clinic. Original written by Joe Dangor. Note: Content may be edited for style and length.

“Our study suggests that maintaining and improving social connections may benefit the oral health of older adults,” said Xiang Qi, a PhD student at NYU Meyers and the study’s first author. “The findings align with previous studies demonstrating that structural indicators of social disconnection can have powerful effects on indicators of health and well-being.”

Social isolation and loneliness in older adults are major public health concerns around the world and are risk factors for heart disease, mental health disorders, cognitive decline, and premature death. In some countries, including the United States and China, up to one in three older adults are lonely, according to the World Health Organization. The COVID-19 pandemic has exacerbated these issues among older adults, as many in-person interactions have been interrupted to protect older adults from infection.

Social isolation and loneliness are related but different. Social isolation is an objective measure defined as having few social relationships or infrequent social contact with others, while loneliness is the feeling created by a lack of social connection.

“While social isolation and loneliness often go hand in hand, it’s possible to live alone and be socially isolated but to not feel lonely, or to be surrounded by people but still feel lonely,” said Bei Wu, Dean’s Professor in Global Health at NYU Meyers and the study’s senior author.

Older adults are also at risk for another health concern: losing teeth. In China, older adults aged 65 to 74 have fewer than 23 teeth on average (adults typically have 32 teeth, or 28 if wisdom teeth have been removed) and 4.5% of this age group has lost all of their teeth. Gum disease, smoking, lack of access to dental care, and chronic illnesses like diabetes and heart disease increase the risks of tooth loss. Missing teeth can have a significant impact on one’s quality of life, affecting nutrition, speech, and self-esteem.

To understand the relationship between social isolation, loneliness, and tooth loss in older adults in China, the researchers used the Chinese Longitudinal Healthy Longevity Survey to analyze data from 4,268 adults aged 65 and up. The participants completed surveys at three different timepoints (2011-12, 2014, and 2018), which captured measures of social isolation and loneliness, how many teeth people had and lost over the 7-year study, and other factors. More than a quarter (27.5%) of the study participants were socially isolated, and 26.5% reported feeling lonely.

The researchers found that higher levels of social isolation were associated with having fewer teeth and losing teeth more quickly over time, even when controlling for other factors such as oral hygiene, health status, smoking and drinking, and loneliness. Older adults who were socially isolated had, on average, 2.1 fewer natural teeth and 1.4 times the rate of losing their teeth than those with stronger social ties.

“Socially isolated older adults tend to be less engaged in social and health-promoting behaviors like physical activity, which could have a negative impact on their overall functioning and oral hygiene, as well as increase their risk for systemic inflammation,” said Wu. “This functional impairment seems to be a major pathway linking social isolation to tooth loss.”

Surprisingly, loneliness was not associated with the number of remaining teeth, nor with the rate of tooth loss.

“While social isolation can result in a lack of support that can affect health behaviors, for older adults who feel lonely, it’s possible that their social networks are still in place and can help them to keep up healthy behaviors,” said Qi.

The findings — which are relevant to countries beyond China, given that social isolation and tooth loss are global issues — highlight the importance of developing interventions to reduce social isolation. Programs could aim to foster intergenerational support within families and improve older adults’ peer and social connections within their local communities.

Additional study authors include Yaolin Pei of NYU Meyers, Katherine Wang of Duke University, and Shuyu Han of Fudan University in China. The research was supported by the National Institute on Aging (1R56AG067619) and the National Institute of Dental and Craniofacial Research (U01DE027512).