Earth

Since its discovery in 2014, phosphorene - a sheet of phosphorus atoms only a single atom thick - has intrigued scientists, due to its unique optoelectronic anisotropy. In other words, electrons interact with light and move in one direction only. This anisotropy means that despite being two dimensional (2D), phosphorene shows a mix of properties found in both one-dimensional (1D) and 2D materials. Scientists believe that the distinct quasi-1D nature of phosphorene could be exploited to develop new, innovative optoelectronic devices, from LEDs to solar cells.

Now, scientists from the Femtosecond Spectroscopy Unit at the Okinawa Institute of Science and Technology Graduate University (OIST) have shed light on how excitons - an excited state of matter at the core of optoelectronics - move and interact within phosphorene.

"Because of the anisotropy, excitons behave in a really unique way in phosphorene compared to other 2D materials, which we are only just beginning to understand," said Vivek Pareek, PhD student and first author of the study, published in Physical Review Letters.

Excitons are formed when a material absorbs a photon of light, causing an electron to be excited to a higher energy state. This leaves a positively charged "hole" where the electron used to reside in its initial energy state, which is attracted to the negatively charged excited electron. The resultant bound electron-hole pair - the exciton - can then move through the material and interact with other excitons.

But excitons are short-lived and in time, the excited electrons "fall" back into the holes. To do so, excitons can either emit a photon - a process called radiative recombination - or they can collide with each other, transferring heat to the material - a non-radiative recombination called exciton-exciton annihilation.

"Exciton-exciton interaction, or annihilation, is very different in 1D and 2D systems," explained Pareek. "We can therefore use exciton-exciton annihilation as a tool to probe the nature of interactions in quasi-1D phosphorene."

Probing phosphorene

The scientists used a laser to send two pulses of light at phosphorene - a pump pulse to excite the electrons to form excitons, and a probe pulse to capture how exciton-exciton annihilation occurred during the first hundred picoseconds, which are trillionths of a second. By changing the power of the pump pulse, the researchers altered the initial density of excitons formed.

The team found that as exciton density increased, exciton-exciton annihilation changed in dimension, shifting from 1D to 2D. The researchers show that this dimensional shift occurred due to phosphorene's anisotropic properties, which arise due to the unusual structure of the material. This anisotropy causes excitons to move more rapidly in one specific direction along the lattice and move more slowly in the other direction. Therefore, at low exciton densities, interactions between excitons predominantly occurred only in one dimension - along the more favorable direction. But when the exciton density was increased, resulting in smaller distances between excitons, interactions started to occur in both dimensions.

The scientists also explored the effect of temperature on exciton-exciton annihilation. When the team cooled down the phosphorene flakes, exciton-exciton annihilation reverted from 2D to 1D, even at high exciton densities.

"This study shows that we can control whether exciton-exciton annihilation occurs in one or two dimensions, depending on conditions we set," said Dr. Julien Madéo, OIST staff scientist and co-author of the study. "This reveals a new interesting property of phosphorene, enhancing its prospects as a new material in optoelectronic devices."

Three new species of toothed pterosaurs -- flying reptiles of the Cretaceous period, some 100 million years ago -- have been identified in Africa by an international team of scientists led by Baylor University.

The pterosaurs, which soared above a world dominated by predators, formed part of an ancient river ecosystem in Africa that teemed with life including fish, crocodiles, turtles and several predatory dinosaurs.

"Pterosaur remains are very rare, with most known from Europe, South America and Asia. These new finds are very exciting and provide a window into the world of pterosaurs in Cretaceous Africa," said lead author Megan L. Jacobs, a doctoral candidate in geosciences at Baylor University.

The study, published in the journal Cretaceous Research, is helping to uncover the poorly known evolutionary history of Africa during the time of the dinosaurs. The research finds that African pterosaurs were quite similar to those found on other continents. Their world included crocodile-like hunters and carnivorous dinosaurs, with few herbivores. Many predators, including the toothed pterosaurs, preyed on a superabundance of fish.

"For such large animals, they would have weighed very little," Jacobs said. "Their wingspans were around 10 to 13 feet, with their bones almost paper-thin and full of air, very similar to birds. This allowed these awesome creatures to reach incredible sizes and still be able to take off and soar the skies."

Pterosaurs snatched up their prey while on the wing, using a set of large spike-like teeth to grab. Large pterosaurs such as these would have been able to forage over hundreds of miles, with fossil evidence showing they flew between South America and Africa, similar to present-day birds such as condors and albatrosses, researchers said.

The specimens -- identified by researchers from chunks of jaws with teeth -- were obtained from fossil miners in a small village called Beggaa, just outside Erfoud in southeast Morocco. These villagers daily climb halfway up the side of a large escarpment, known as the Kem Kem beds, to a layer of a coarse sand, the most fossiliferous bed.

"They excavate everything they find, from teeth to bones to almost complete skeletons," Jacobs said. "They then sell their finds to dealers and scientists who conduct fieldwork, ensuring the villagers make enough money to survive while we get new fossils to describe. These pterosaur fragments are unique and can be identified easily -- if you know what to look for."

One of the species, Anhanguera, previously was only known to be from Brazil. Another, Ornithocheirus, had until now only been found in England and Middle Asia.

This year's find brings to five the total of toothed pterosaurs whose remains have been found in the Kem Kem beds, with the first described in the 1990s and the second one last year, Jacobs said. The specimens will be part of an acquisition in a museum in Morocco.

Novel, fully digital, high-resolution positron emission tomography/computed tomography (PET/CT) imaging of small brain stem nuclei can provide clinicians with valuable information concerning the auditory pathway in patients with hearing impairment, according to a new study published in the March issue of The Journal of Nuclear Medicine. Using 18F-FDG PET/CT imaging, researchers found that patients with asymmetrical hearing loss have reduced glucose metabolism in parts of the brain stem and primary auditory cortex. The latter may be influenced by cortical reorganization and thus, hopefully help to predict the chance that a cochlear implant will improve hearing.

"With the possible exception of few dedicated high-resolution research scanners, earlier PET/CT systems with lower resolution did not permit clear-cut identification and assessment of brain stem nuclei," said Iva Speck, MD, resident of otorhinolaryngology at the University of Freiburg Medical Center in Freiberg, Germany. "Today, the use of fully digital clinical PET/CT systems permits greatly enhanced imaging and quantitative assessment of small brain stem nuclei, such as the inferior colliculus (IC), the part of the midbrain that acts as a main auditory pathway for the body."

In the study, 13 patients with asymmetric hearing loss underwent 18F-FDG PET/CT imaging. The scans were reviewed by two experienced readers who examined regional glucose metabolism in the IC and the primary auditory cortex (PAC)--a part of the brain known to undergo metabolic changes based on acoustical outside input and transformation to neuronal signals from the cochlea hair cells to the auditory nerve fibers. The readers rated the scans as to whether glucose metabolism showed no asymmetry or mild, moderate or strong asymmetry to the left or to the right for the IC and PAC separately. Statistical analyses were performed to determine the effect of the duration of hearing impairment on glucose metabolism and to compare glucose metabolism between the IC and PAC.

Regional glucose metabolism of both the IC and PAC was significantly reduced on the contralateral (opposite) side of the poorer-hearing ear, as compared to the ipsilateral (same) side. In addition, a longer duration of hearing impairment was associated with a higher metabolism on the contralateral PAC. By contrast, duration of hearing impairment did not predict regional glucose metabolism for the ipsilateral PAC or either side of the IC.

"Previous studies suggest that the association between longer duration of hearing impairment and higher glucose metabolism indicates cortical reorganization. In bilateral deaf patients this has been shown to lessen the benefits of cochlear implants," said Speck. "Prediction of a successful cochlear implant outcome might benefit from improved imaging with fully digital PET/CT systems, as large parts of the auditory system, including small brain nuclei such as the IC, can be assessed for preoperative patient characterization."

She continued, "Beyond this topic, the study's findings are of interest for other neurological research fields, like neurodegenerative diseases, which often affect brain stem nuclei early in disease course," Speck remarked. "Digital PET pushes the limits of what can be imaged and contributed to patient care by molecular imaging."

Tohoku University researchers in Japan have uncovered a molecular link between some trans fats and a variety of disorders, including cardiovascular and neurodegenerative diseases. Their findings, published in the journal Scientific Reports, implicate their role in enhancing a mitochondrial signalling pathway that leads to programmed cell death.

"Accumulating evidence has associated the consumption of trans-fatty acids with various diseases, including some lifestyle diseases, atherosclerosis and dementia. But the underlying causes have remained largely unknown," says Atsushi Matsuzawa of Tohoku University's Laboratory of Health Chemistry.

Matsuzawa and a team of researchers explored the effects of two trans fats produced during industrial food manufacturing, elaidic and linoelaidic acids, on programmed cell death.

Cells instigate programmed cell death, which is called apoptosis, if their DNA is damaged beyond repair. DNA damage can occur in response to a variety of factors, including reactive oxygen species, ultraviolet irradiation and anti-cancer drugs. Normally, cells counteract this process by repairing the lesions. But problems in the DNA damage response can lead to diseases also associated with trans fats.

The researchers induced DNA damage in cells using the anti-cancer drug doxorubicin. They found that elaidic and linoelaidic acids enhanced the apoptosis that followed. Other unsaturated fatty acids did not have the same effect.

Specifically, they found the fatty acids affected mitochondria, the energy-generating powerhouses of cells. DNA damage activates a signalling loop inside mitochondria that generates reactive oxygen species, which ultimately promote apoptosis. The industrial trans fats enhanced mitochondria's production of reactive oxygen species through this signalling loop, and thus increased apoptosis.

Apoptosis is thought to lead to the development and progression of disorders associated with industrial trans fats, such as the build-up of plaque inside arteries, called atherosclerosis.

"Our research revealed a novel toxic function and mechanism of action of trans-fatty acids, which can account for pathological mechanisms, including atherosclerosis," says Matsuzawa. "This significant finding will provide a molecular basis to understand how trans-fatty acids cause disease."

The researchers theorize that targeting this molecular mechanism with drugs might have a therapeutic effect on a diverse range of trans-fat-associated diseases. The team plans to further investigate this link and the extent to which this mechanism contributes to these diseases. They also aim to determine the differences in toxicity between different trans fats.

Regular tub bathing is linked to a lower risk of death from heart disease and stroke, indicates a long term study, published online in the journal Heart.

And the higher the 'dose,' the better it seems to be for cardiovascular health, with a daily hot bath seemingly more protective than a once or twice weekly one, the findings indicate.

A linked editorial sounds a note of caution, however, because sudden death associated with hot baths is relatively common in Japan, where the study was conducted.

Having a bath is associated with good sleep quality and better self-rated health, but it's not clear what its long term impact might be on cardiovascular disease risk, including heart attack, sudden cardiac death, and stroke.

To explore this further, the researchers drew on participants in The Japan Public Health Center based Study Cohort 1, a population based tracking study of more than 61,000 middle aged adults (45 to 59 years).

At the start of the study in 1990, some 43,000 participants completed a detailed questionnaire on their bathing habits and potentially influential factors: lifestyle, to include exercise, diet, alcohol intake, weight (BMI); average sleep duration; and medical history and current medicines use.

Each participant was monitored until death or completion of the study at the end of December 2009, whichever came first, with the final analysis based on 30,076 people.

During the monitoring period, 2097 cases of cardiovascular disease occurred: 275 heart attacks; 53 sudden cardiac deaths; and 1769 strokes.

After taking account of potentially influential factors, analysis of the data showed that compared with a once or twice weekly bath or no bath at all, a daily hot bath was associated with a 28% lower overall risk of cardiovascular disease, and a 26% lower overall risk of stroke.

The frequency of tub bathing wasn't associated with a heightened risk of sudden cardiac death, or with a particular type of stroke, called subarachnoid haemorrhage (bleed into the space surrounding the brain).

Further analysis of preferred water temperature indicated 26% lower and 35% lower risks of overall cardiovascular disease for warm and hot water, respectively. But no significant associations emerged for overall stroke risk and water temperature.

After excluding those participants who developed cardiovascular disease within 5 or 10 years of the start of the study, the associations found weren't quite as strong, but nevertheless still remained statistically significant.

This is an observational study, and as such, can't establish cause, added to which changes in bathing frequency weren't tracked during the monitoring period. The typical style of Japanese bathing also includes immersion to shoulder height, and this may be a critical factor.

But, say the researchers, previously published research has pointed to a link between heat exposure and cardiovascular disease prevention: this is because the effects of heat on the body are not dissimilar to those of exercise.

"We found that frequent tub bathing was significantly associated with a lower risk of hypertension, suggesting that a beneficial effect of tub bathing on risk of [cardiovascular disease] may in part be due to a reduced risk of developing hypertension," write the researchers.

They acknowledge that taking a hot bath is not without its risk, particularly if the temperature is too high, a point that is taken up by Dr Andrew Felix Burden in a linked editorial.

"There can be no doubt about the potential dangers of bathing in hot water, and the occurrence of death from this increases with age, as well as with the temperature of the water," he writes.

Although cardiovascular disease itself is unlikely to be the cause of these deaths, overheating, leading to confusion and drowning, most likely is, he suggests.

"Investigations into the potential cardiovascular benefit of heat-free immersion in warm to hot water are needed," he says. "In the meanwhile, caution is needed because of the higher mortality associated with such bathing in an unselected population."

Despite fundamental differences in their biology, plants and animals are surprisingly similar in how they have evolved in response to climate around the world, according to a new study published this week in Nature Ecology and Evolution.

Plants and animals are fundamentally different in many ways, but one of the most obvious is in how they deal with temperature.

"When it gets sunny and hot where they are at a given moment, most animals can simply move to find some shade and cool down," said lead study author John J. Wiens, a professor of ecology and evolutionary biology at the University of Arizona. "Plants on the other hand, have to stay where they are and tolerate these higher temperatures."

Together with Hui Liu and Quing Ye from the South China Botanical Garden, Wiens analyzed climatic data from 952 plant species and 1,135 vertebrate species. They included many major groups of flowering plants, from oaks to orchids to grasses, and all major groups of terrestrial vertebrates including frogs, salamanders, lizards, snakes, turtles, crocodilians, birds and mammals.

The team used climatic data and detailed evolutionary trees to test 10 hypotheses about the temperature and precipitation conditions where each species occurs and how these change over time among species. This set of conditions is also known as the "climatic niche" of each species.

The climatic niche of a species reflects where it can live, Wiens explained - for example, in the tropics versus the temperate zone, or at sea level versus the top of a mountain - and how it will respond to climate change.

A species with a wide climatic niche can range widely across many different conditions and may be especially resilient to climate change. A species with a narrow niche, on the other hand, may have a small distribution and may be especially vulnerable to climate change. Understanding climatic niches is critically important for answering many of the most fundamental and urgent questions in ecology and evolution.

For all 10 hypotheses the authors tested, they found that plants and animals showed similar patterns of niche evolution. For example, on average, each plant and animal species lives across a similar breadth of environmental conditions. The breadth of conditions that each species lives in also changes in the same way across the globe in both groups, with plant and animal species in tropical regions found in only a narrow range of temperatures and those in temperate zones tolerating a broad range of temperatures. Furthermore, climatic niches of plants and animals change at similar rates over time.

These results can help explain many fundamental patterns in nature. For example, different sets of plant and animal species tend to occur at different elevations, which differ in temperature and precipitation. In the southwestern United States, for example, different elevations are home to different sets of plant and animal species, from low-lying deserts to grasslands to oak woodlands to pine forests to spruce-fir forests at the higher elevations.

"Since each plant and animal species tolerates a similar, limited breadth of climatic conditions - on average - you end up with different sets of both plant and animal species at different elevations along a mountain slope," Wiens explained.

These findings may also help explain why different sets of species occur in temperate regions and tropical regions in both groups, and why plants and animals tend to have biodiversity hotspots and high species numbers in the same places - for example, the Andes mountains of South America.

The study also suggests how future climate change may impact plant and animal species.

"The finding that plants and animals have similar niche breadths and rates may help explain why local extinctions from climate change have occurred at similar frequencies in plants and animals so far, and why similar levels of species extinction are predicted for both groups in the future," said Wiens. "Species with broader niches and faster rates may be better able to survive climate change over the next 50 years, and niche breadths and rates are very similar between plants and animals overall."

Furthermore, the finding that species are adapted to a narrower range of temperatures in the tropics helps explain why a higher frequency of extinctions is predicted there than in the temperate zone, even though warming may be similar or even greater at higher latitudes.

The authors also found that in both plants and animals, species seem to have more difficulty adapting rapidly to hotter temperatures and drier conditions than to cooler and wetter conditions. Therefore, both plants and animals may have a particularly difficult time adapting to increasing temperatures and droughts related to global warming.

DURHAM, N.C. -- Scientists have devised a simple new model that explains how the undesirable effects of urban heat islands vary across seasons. Their results could help cities in different climatic regions design heat mitigation strategies.

Unlike existing urban climate models which require a large amount of information and are computationally very demanding, the new coarse-grained model provides general insights into how seasonal changes in rainfall, solar radiation, and vegetation conditions of an urban environment affects the intensity and timing of surface urban heat islands at a city-wide scale.

"With just two equations, our model can describe all these complex interactions," said Gabriele Manoli, a lecturer in environmental engineering at University College London, who led the research.

"For city planners, it provides a new approach that complements more detailed, city-specific tools, and provides general guidelines on the effects of heat mitigation strategies, such as increasing green spaces, in different climates and during different times of the year," Manoli said. "Because of its simplicity, our framework can be applied to cities where extensive data and detailed simulations are not available."

For scientists, the model provides new evidence that seasonal variations in the intensity of urban-rural surface temperature differences -- which, until now, have been observed but not clearly explained -- are controlled by time lags between solar radiation, temperatures, and rainfall, Manoli said.

If solar radiation occurs in conjunction with water availability, summer conditions cause strong surface urban heat island intensities due to high rates of evaporative cooling in surrounding rural areas. The rural areas grow cooler by a few degrees, while the urban area, where impervious and heat-absorbing surfaces can limit the effect of evaporative cooling, grows much warmer. This is typically what we see in cities like Paris or London, which are in climates with relatively wet summers.

"This can have major implications for local energy consumption, climate adaptation policies, and public health, especially heat-related mortalities," said Gabriel Katul, Theodore S. Coile Distinguished Professor of Hydrology and Micrometeorology at Duke University.

But in cities where rainfall is scarce during summer, such as Phoenix or Madrid, the opposite effect can occur. With less rainfall and vegetation to spur cooling, rural areas heat up and the city experiences an "oasis effect" in which, though it may still be blisteringly hot, it's nonetheless one or two degrees cooler than the surrounding countryside.

"These seasonal patterns of warming and cooling have significant implications for heat mitigation strategies, as urban green spaces can reduce heat island intensity during summer, while potentially negative effects during winter of albedo management, e.g. painting streets of white, are mitigated by the seasonality of solar radiation," Katul noted.

Rising temperatures and shifting rainfall patterns linked to climate change may alter the seasonality of urban heat islands in coming decades, he said. Further research is needed in that direction.

Manoli and Katul developed the new model with Simone Fatichi of ETH Zurich and Elie Bou-Zeid of Princeton University.

Rats with regular access to cannabis seek more of the substance and tend to show increased drug-seeking behavior when cannabis is absent.

That's according to a new study conducted by neuroscientists in Washington State University's Integrative Physiology and Neuroscience unit.

The research, published in the Journal of Neuroscience, is the next step to better understand the cognitive and neural effects of cannabis use in humans.

"It's always difficult to establish reliable cannabis-seeking behavior using animal models. In this study we have a clear and reliable response for cannabis by utilizing the very first self-administration model involving on-demand delivery of whole-plant cannabis vapor," said Ryan McLaughlin, professor in WSU's Integrative Physiology and Neuroscience unit.

So, how do you give a rat the option to self-administer cannabis?

Well, their curious nose, of course.

WSU researchers trained male Sprague Dawley rats to poke their nose into a small port within a Plexiglas chamber with constant air flow to automatically deliver discrete "puffs" of whole-plant cannabis vapor.

The chambers are equipped with a spigot that delivers vapor, a cue light that illuminates during vapor delivery, an exhaust system for vapor evacuation, and two small nose poke ports, one of which activates a three-second puff of cannabis vapor.

Animals were able to administer puffs of whole-plant, tetrahydrocannabinol-rich (THC) cannabis vapor during daily one-hour sessions over the course of 21 days. Another group of rats received cannabidiol-rich (CBD) cannabis vapor, and a control group received vapor not containing any cannabinoids.

"By the third day of the study, animals began to establish associations between their nose pokes and the cannabis vapor delivery," McLaughlin said.

Animals exposed to THC-rich cannabis vapor administered more vapor deliveries than the other two study groups from day four to day 21, sometimes doubling the number of deliveries to each group.

What was more shocking was when cannabis was taken away on day 22.

"They would show a burst in responding," McLaughlin said. "It went from 17 to 18 nose pokes up to 70 or 80 on average. They were trying to figure out why it wasn't working."

In addition, drug-paired cues also increased the animals' response rates.

For example, researchers found an increase in nose poke responses when the cue light was introduced following an extended absence of THC-rich vapor delivery.

"It was similar to when you have someone who has stopped smoking cannabis for a while but then sees their pipe or their vape pen, immediately that cue makes them want to seek that drug again," Tim Freels, post-doctoral researcher and first author on the paper, said.

The researchers found that food intake was higher, and activity was lower for the animals exposed to THC-rich vapor, yet they expended more energy and burned more calories than the other two groups.

"They experienced a lot of the same effects people would experience," Freels said. "And that is very important when you're trying to validate a model and then extend it to a human population."

Up until the use of this new self-administration model, it was difficult to compare previous cannabis research in animals with the human condition, as most animal-cannabis studies involved an injection of THC or synthetic cannabinoids rather than giving the animal the option to self-administer whole-plant cannabis vapor.

For the McLaughlin Lab, the next steps are to look at the long-term effects of cannabis vapor self-administration during sensitive developmental periods, such as pregnancy or adolescence.

"We urgently need more information on the effects of cannabis use on the developing brain, and this model will be important for identifying potential risks that can be relayed to human cannabis users," McLaughlin said.

Changes in a specific type of sugarlike molecule, or glycan, on the surface of cancer cells help them to spread into other tissues, according to researchers at the University of California, Davis. Published March 23 in Proceedings of the National Academy of Sciences, the work could lead to diagnostic tests and new therapies to slow or stop the spread of cancers.

The research team led by Professor Carlito Lebrilla, UC Davis Department of Chemistry, worked with cells derived from a human cholangiocarcinoma, or bile duct cancer. Cholangiocarcinoma is relatively rare but becoming more common in the U.S. It metastasizes readily and is often incurable by the time of diagnosis.

Generally, researchers have studied how cancer cells spread by looking at the proteins on their surface membranes. Some of these proteins may serve as receptors that engage with other cells, allowing cancerous cells to attach and move into tissues.

But proteins on living cells are also coated with a wide variety of sugarlike carbohydrate molecules called glycans. These glycans modify how proteins -- and therefore the cells -- interact with their environment. While DNA dictates the protein's structure, glycans and carbohydrates are made and metabolized by the protein's own machinery. That makes studying these molecules even more challenging.

Lebrilla's laboratory at UC Davis has been studying glycans, glycoproteins and the roles they play in the body for many years, developing new techniques to analyze and characterize them.

How glycans modify proteins

Metastatic cholangiocarcinoma cells had high levels of the glycan mannose on surface proteins, Lebrilla's team discovered. These cancer cells lacked the gene for an enzyme that breaks down mannose. The presence of mannose was associated with cancer cells being able to spread out on a dish and migrate through pores in a membrane, simulating squeezing through the wall of a blood vessel into surrounding tissue.

"What is interesting here is that it's a new way to look at cancer metastasis. Instead of looking at proteins, we've looked at how protein modifications are affecting the metastatic behavior of cancer cells," Lebrilla said.

If modified glycans are a characteristic of metastatic cancers, that could present a new way to diagnose cancer and perhaps predict which cancers are likely to become invasive. The glycans and the metabolic pathways that make them could also be targets for new drugs.

WASHINGTON, March 24, 2020 -- Biohydrogels -- biomaterials composed of polymer chains dispersed in water -- have been studied closely by researchers for their potential use in biomedical applications, such as in tissue repair, as surgical sealants, and in 3D biofabrication.

Since these gels contain particles in the solid state that are dispersed as molecules in the liquid state, they often move between sols (the liquid form of a colloid) and gels (the soft solid form of a colloid), depending on whether they are at room or body temperature. These changes can pose issues depending on their intended use.

In this week's Physics of Fluids, from AIP Publishing, researchers in New Zealand, Canada and the United States studied the effect of temperature on hydrogels. They found that creating hydrogels at room temperature or below results in more robust materials that function more effectively when used in the body.

"When we want to create a patch for a lung puncture, we want something that can biodegrade in the body but is, at the same time, very sticky, so it adheres to the lung and is tough, so it can work as the lung expands and shrinks," said author Heon Park, at the University of Canterbury.

The findings could be very useful in the 3D printing of biomaterials. When printing tissues, such as a piece of a lung, or printing artificial material, such as dialysis membrane, bioink (hydrogel plus cells) is currently stored in a syringe barrel, and it flows out of the syringe through a nozzle by squeezing a piston.

The authors demonstrate that the bioink will flow irregularly like a gel through the nozzle, if the nozzle or the barrel is at room temperature, and this will result in a printed part that is out of shape.

"Our research also shows the temperature of the bioink in the printing syringe should be at body temperature, so that it flows easily when it emerges, and that the printing bed should be room temperature or below, so that the printed part toughens," said Park.

The researchers also discovered methods for minimizing drying of hydrogels, a problem uncovered in many current studies.

"Big picture, we have shown that the best way to engineer biomaterials that are rigid and sticky is by changing the temperature rather than by reformulating the hydrogels," said Park.

What The Study Did: This observational study used national survey data from young people up to age 19 to estimate the overall diet quality of children and teens in the United States and to explore how diet quality has changed from 1999 to 2016.

Authors: Junxiu Liu, Ph.D., of Tufts University in Boston, is the corresponding author.

To access the embargoed study: Visit our For The Media website at this link https://media.jamanetwork.com/ 

(doi:10.1001/jama.2020.0878)

Editor's Note: The article includes conflict of interest and funding/support disclosures. Please see the articles for additional information, including other authors, author contributions and affiliations, conflicts of interest and financial disclosures, and funding and support.

WASHINGTON, March 24, 2020 -- During the 1990s, Carver Mead and colleagues combined basic research in neuroscience with elegant analog circuit design in electronic engineering. This pioneering work on neuromorphic electronic circuits inspired researchers in Germany and Switzerland to explore the possibility of reproducing the physics of real neural circuits by using the physics of silicon.

The field of "brain-mimicking" neuromorphic electronics shows great potential not only for basic research but also for commercial exploitation of always-on edge computing and "internet of things" applications.

In Applied Physics Letters, from AIP Publishing, Elisabetta Chicca, from Bielefeld University, and Giacomo Indiveri, from the University of Zurich and ETH Zurich, present their work to understand how neural processing systems in biology carry out computation, as well as a recipe to reproduce these computing principles in mixed signal analog/digital electronics and novel materials.

One of the most distinctive computational features of neural networks is learning, so Chicca and Indiveri are particularly interested in reproducing the adaptive and plastic properties of real synapses. They used both standard complementary metal-oxide semiconductor (CMOS) electronic circuits and advanced nanoscale memory technologies, such as memristive devices¬, to build intelligent systems that can learn.

This work is significant, because it can lead to a better understanding of how to implement sophisticated signal processing using extremely low-power and compact devices.

Their key findings are that the apparent disadvantages of these low-power computing technologies, mainly related to low precision, high sensitivity to noise and high variability, can actually be exploited to perform robust and efficient computation, very much like the brain can use highly variable and noisy neurons to implement robust behavior.

The researchers said it is surprising to see the field of memory technologies, typically concerned with bit-precise high-density device technologies, now looking at animal brains as a source of inspiration for understanding how to build adaptive and robust neural processing systems. It is very much in line with the basic research agenda that Mead and colleagues were following more than 30 years ago.

"The electronic neural processing systems that we build are not intended to compete with the powerful and accurate artificial intelligence systems that run on power-hungry large computer clusters for natural language processing or high-resolution image recognition and classification," said Chicca.

In contrast, their systems "offer promising solutions for those applications that require compact and very low-power (submilliwatt) real-time processing with short latencies," Indiveri said.

He said examples of such applications fall within "the 'extreme-edge computing' domain, which require a small amount of artificial intelligence to extract information from live or streaming sensory signals, such as for bio-signal processing in wearable devices, brain-machine interfaces and always-on environmental monitoring."

A container ship leaves a trail of white clouds in its wake that can linger in the air for hours. This puffy line is not just exhaust from the engine, but a change in the clouds that's caused by small airborne particles of pollution.

New research led by the University of Washington is the first to measure this phenomenon's effect over years and at a regional scale. Satellite data over a shipping lane in the south Atlantic show that the ships modify clouds to block an additional 2 Watts of solar energy, on average, from reaching each square meter of ocean surface near the shipping lane.

The result implies that globally, cloud changes caused by particles from all forms of industrial pollution block 1 Watt of solar energy per square meter of Earth's surface, masking almost a third of the present-day warming from greenhouse gases. The open-access study was published March 24 in AGU Advances, a journal of the American Geophysical Union.

"In climate models, if you simulate the world with sulfur emissions from shipping, and you simulate the world without these emissions, there is a pretty sizable cooling effect from changes in the model clouds due to shipping," said first author Michael Diamond, a UW doctoral student in atmospheric sciences. "But because there's so much natural variability it's been hard to see this effect in observations of the real world."

The new study uses observations from 2003 to 2015 in spring, the cloudiest season, over the shipping route between Europe and South Africa. This path is also part of a popular open-ocean shipping route between Europe and Asia.

Small particles in exhaust from burning fossil fuels creates "seeds" on which water vapor in the air can condense into cloud droplets. More particles of airborne sulfate or other material leads to clouds with more small droplets, compared to the same amount of water condensed into fewer, bigger droplets. This makes the clouds brighter, or more reflective.

Past attempts to measure this effect from ships had focused on places where the wind blows across the shipping lane, in order to compare the "clean" area upwind with the "polluted" area downstream. But in this study researchers focused on an area that had previously been excluded: a place where the wind blows along the shipping lane, keeping pollution concentrated in that small area.

The study analyzed cloud properties detected over 12 years by the MODIS instrument on NASA satellites and the amount of reflected sunlight at the top of the atmosphere from the CERES group of satellite instruments. The authors compared cloud properties inside the shipping route with an estimate of what those cloud properties would have been in the absence of shipping based on statistics from nearby, unpolluted areas.

"The difference inside the shipping lane is small enough that we need about six years of data to confirm that it is real," said co-author Hannah Director, a UW doctoral student in statistics. "However, if this small change occurred worldwide, it would be enough to affect global temperatures."

Once they could measure the ship emissions' effect on solar radiation, the researchers used that number to estimate how much cloud brightening from all industrial pollution has affected the climate overall.

Averaged globally, they found changes in low clouds due to pollution from all sources block 1 Watt per square meter of solar energy -- compared to the roughly 3 Watts per square meter trapped today by the greenhouse gases also emitted by industrial activities. In other words, without the cooling effect of pollution-seeded clouds, Earth might have already warmed by 1.5 degrees Celsius (2.7 F), a change that the Intergovernmental Panel on Climate Change projects would have significant societal impacts. (For comparison, today the Earth is estimated to have warmed by approximately 1 C (1.8 F) since the late 1800s.)

"I think the biggest contribution of this study is our ability to generalize, to calculate a global assessment of the overall impact of sulfate pollution on low clouds," said co-author Rob Wood, a UW professor of atmospheric sciences.

The results also have implications for one possible mechanism of deliberate climate intervention. They suggest that strategies to temporarily slow global warming by spraying salt particles to make low-level marine clouds more reflective, known as marine cloud brightening, might be effective. But they also imply these changes could take years to be easily observed.

"What this study doesn't tell us at all is: Is marine cloud brightening a good idea? Should we do it? There's a lot more research that needs to go into that, including from the social sciences and humanities," Diamond said. "It does tell us that these effects are possible -- and on a more cautionary note, that these effects might be difficult to confidently detect."

With over 300,000 COVID-19 cases across the globe, including recent cases in Syria and the Gaza Strip, the data continues to demonstrate how the disease has no borders. A new Dartmouth-led commentary in the International Journal for Equity in Health highlights how people affected by humanitarian crises are especially vulnerable to COVID-19.

According to United Nations estimates, in 2020, "over 168 million worldwide will need humanitarian assistance and protection." Many people experiencing humanitarian crises, often due to conflicts or natural disasters, lack access to basic needs, including food, shelter and healthcare. As the co-authors point out in their commentary, these communities do not have "the infrastructure, support and health systems" to institute a comprehensive, public health response. These are places, which may have very little, if any health infrastructure-- communities, which may not have any trained medical personnel or personal protective equipment.

"The World Health Organization's basic protective measures against COVID-19, include washing your hands frequently; yet, access to soap and clean water is not typically an option for people living in humanitarian crises," explains lead author Danielle M. Poole, a Neukom fellow in the department of geography at Dartmouth. "These are populations that do not have adequate water, sanitation and hygiene (WASH) tools."

Past research however, has demonstrated how making soap available to households in humanitarian settings can increase handwashing by 30 percent.

"Regarding COVID-19, maintaining social distancing or one meter (three feet) from someone coughing or sneezing, may also prove challenging for crises-affected populations, who typically live in overcrowded conditions," added Poole. "With overcrowded living conditions, separating the exposed from the healthy and creating spaces for quarantine, will also be especially difficult without critical humanitarian assistance."

To prepare for COVID-19 in humanitarian crisis areas, the co-authors call on national governments and international organizations to develop mitigation strategies and draw on best global practices from evidence-based approaches to fighting respiratory viruses.

Danielle Poole is available for comment at: dani.poole@dartmouth.edu. She has observed the complexities of addressing public health in a humanitarian crisis, as she spent time the past four years leading research to improve health among displaced populations in refugee camp and urban settings in Greece, Kenya, Italy, and Turkey.

Although most cancer cells are killed by chemotherapy, individual cells vary in their sensitivity, so that some cancer cells often escape. Diversity among cancer cells is thus an issue for cancer treatment.

Previously diversity was thought to be mostly due to genetic variability among cancer cells. Now, however, University of Sydney researchers have discovered a whole new source of cancer cell diversity, with profound implications for cancer treatment.

In 2012, a team led by Professor Hans Zoellner from the University of Sydney School of Dentistry, published that cancer cells exchange contents with surrounding normal cells called fibroblasts , but the mechanism remained unknown, until now.

The results published today in Biophysical Journal by Zoellner's team, finally explain how. (Preprint of Biophysical Journal Article)

All cells constantly probe each other with tentacle-like cell-projections. These reach out to neighbours, probe, and then retract, as part of the way cells sense their environment. When a cell-projection retracts, there is a brief increase in fluid pressure within the projection, to force cytoplasm - the jelly-like fluid within the cells - back into the cell body.

Studying cells in time-lapse movies, Professor Zoellner noticed that transfer is from retracting cell-projections.

He reasoned that transient micro-fusions between the retracting cell-projections and any neighbouring cell, would permit cytoplasm from the cell-projection to be injected into the neighbour, instead of being returned to the fibroblast (Cartoon Image of Cell-Projection Pumping and Explanation).

Working in both Sydney at the Faculty of Medicine and Health and on sabbatical in New York's Memorial Sloan Kettering Cancer Center, Zoellner and his team tested this idea by combining mathematical modelling, cell experimentation, and computer simulation. The outcome, is discovery of what seems a previously unknown biological mechanism, now coined 'cell-projection pumping' (Preprint of Biophysical Journal Article).

Cancer cells become more aggressive after cell-projection pumping

The significance of cell-projection pumping is underscored by separate work published by Professor Zoellner's team, also in collaboration with Memorial Sloan-Kettering Cancer Center. They found that cancer cells become more diverse in size and shape, and also migrate more quickly, after cell-projection pumping . Importantly, preliminary results show a further effect, resisting chemotherapy.

The work continues, and Zoellner says: "This is a whole new cancer target. Now that we know it's happening, we can think about trying to block it, and work towards better outcomes.

"This has been a tough project, stretched over 19 years, and very hard to fund, but I'm glad to have such wonderful colleagues, and proud of my team's persistence".