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DURHAM, N.H.-- Researchers at the University of New Hampshire have identified new pathways in an RNA-based virus where inhibitors, like medical treatments, unbind. The finding could be beneficial in understanding how these inhibitors react and potentially help develop a new generation of drugs to target viruses with high death rates, like HIV-1, Zika, Ebola and SARS-CoV2, the virus that causes COVID-19.

"When we first started this research, we never anticipated that we'd be in the midst of a pandemic caused by an RNA virus," said Harish Vashisth, associate professor of chemical engineering. "But as these types of viruses emerge our findings will hopefully offer an enhanced understanding of how viral RNAs interact with inhibitors and be used to design better treatments."

Similar to how humans are made up of a series of different chromosomes, known as DNA, many viruses have a genetic makeup of RNA molecules. These RNA-based genomes contain potential sites where inhibitors can attach and deactivate the virus. Part of the challenge in drug development can be fluctuations in the viral genome that may prevent the inhibitors from attaching.

In their paper, recently published in the Journal of Physical Chemistry Letters, the researchers looked specifically at an RNA fragment from the HIV-1 virus and its interaction with a ligand/inhibitor, a complex compound that is known to interfere with the virus replication process. Using computer modeling, the researchers discovered the pathways of the inhibitor unbinding from the viral RNA in several rare events that unexpectedly showed a coordinated movement in many parts of the binding pocket that are the building blocks of RNA. The scientists focused on the structural elements from the HIV-1 RNA genome because they are considered a good model for studying the same processes across a wide range of RNA viruses. The researchers conducted simulations at the molecular level of the rare structural and conformational actions of the binding/unbinding process which are often difficult to observe using experimental methods in the lab.

"We observed what are called rare base-flipping events involved in the inhibitor binding/unbinding process that provided the new details of the underlying mechanism of this process," said Vashisth. "Our hope is that this adds new possibilities to a field traditionally focused on static biomolecular structures and lead to new medications."

The whitespotted eagle ray (Aetobatus narinari), found in estuaries and lagoons throughout Florida, is listed as "near threatened" on the International Union for Conservation of Nature's "Red List of Threatened Species." Keeping tabs on this highly mobile species for conservation efforts can be extremely challenging, especially for extended periods of time.

Researchers from Florida Atlantic University's Harbor Branch Oceanographic Institute used uniquely coded transmitters and acoustic telemetry to give them a leading edge to unravel fine-scale movement, behavior, and habitat use of whitespotted eagle rays in Florida's Indian River Lagoon. Biotelemetry provided the researchers with unique insights into this species' occupancy, which is not apparent at the landscape-scale.

Despite being a state-protected species in Florida for more than two decades, this study is the first to characterize the ecology and fine-scale habitat use of whitespotted rays in Florida while also identifying areas of potential interactions between this species and multiple environmental threats. For the study, researchers followed seven mature individuals (six males and one female) and individually tracked them for a total of 119.6 hours. They used a tracking vessel to continuously and manually track the rays between June 2017 and August 2018.

Results of the study, published in the journal Endangered Species Research, show that rays use the deeper portions of the Indian River Lagoon, along Florida's southeast coast, during the day and shallower portions during the night. In addition, they move faster while in the ocean and lagoonal habitats and slower in channels and inlets. This information suggests that whitespotted eagle rays may spend more time foraging at night in the shallow water of the lagoon than during the daytime. These prolonged observations revealed affinities for habitats of considerable recreational and commercial importance, such as inlets, channels, and clam aquaculture lease sites close to shore.

"Understanding channel use is crucial to evaluating risks and potentially developing strategies to mitigate negative impacts to the whitespotted eagle ray, as both channel and inlet habitats have high levels of human activity such as boating and fishing and are prone to coastal development impacts from dredging," said Breanna DeGroot, M.S., lead author, research technician and former graduate student working with Matt Ajemian, Ph.D., co-author and an assistant research professor at FAU's Harbor Branch. "In addition, these high traffic areas experience increased noise and chemical pollution."

Rays also spent a larger proportion of time in the channels and inlet during the lighter and warmer portions of the day and used shallower depths during the cooler and darker portions of the day. Rate of movement significantly increased with temperature, suggesting that rays are more active during warmer periods. While previous studies have found that whitespotted eagle rays are influenced by tidal cycles, this study did not find any tidal patterns in ray habitat use or distribution.

Because more clammers work on lease sites during the day, interactions between the rays and growout sites may therefore be underestimated. Findings from this study will help to inform statewide conservation plans for the species and provide critical information to hard clam aquaculture farmers and restoration managers for the successful production of bivalves in the area.

"As coastal populations and development increase, there is more potential for whitespotted eagle rays to interact with human activities," said Ajemian. "In addition, intense coastal development such as dredging, construction, and pollution have been linked to habitat alteration, which may change the abundance and distribution of this species as has been documented with shark species in degraded habitats."

As whitespotted eagle rays already display an affinity for these modified habitats, increased interactions with humans and added pollution and/or disturbances could result in changes to the species' movement patterns and health. Ultimately, such human-induced habitat alterations could reduce the overall productivity of estuarine areas and, with time, exacerbate pressures already facing populations of aetobatid rays.

Antibiotic treatment in early life impedes brain signalling pathways that function in social behaviour and pain regulation in mice, a new study by Dr Katerina Johnson and Dr Philip Burnet has found. It was published today in BMC Neuroscience.

Katerina Johnson, from the University's Departments of Psychiatry and Experimental Psychology, was researching the effects of disrupting the microbiome on the brain in mice. 'We know from previous research that animals missing microbes, such as germ-free animals (which are devoid of microbes) or antibiotic-treated animals (whose microbes are severely depleted), have impaired social behaviour,' she explains. 'I was therefore particularly interested in the effects of the microbiome on endorphin, oxytocin and vasopressin signalling since these neuropeptides play an important role in social and emotional behaviour.'

The most striking finding was in young animals treated with antibiotics. This resulted in reduced expression of the receptors which mediate endorphin, oxytocin and vasopressin signalling in the frontal cortex. Dr Johnson commented, 'If these signalling pathways are less active, this may help explain the behavioural deficits seen in antibiotic-treated animals. Whilst this study was in animals given a potent antibiotic cocktail, this finding highlights the potential detrimental effects that antibiotic exposure may have on the brain when it's still developing.'

Dr Burnet added, 'Our research underlines the growing consensus that disturbing the microbiome during development can have significant impacts on physiology, including the brain.'

The study was conducted using a relatively small number of animals with high doses of antibiotics and further research should follow up this finding given society's reliance on antibiotics, though of course they still play a vital role in medicine to fight bacterial infections.

This was also the first study to investigate whether the microbiome affects the brain's endorphin system (where endorphin activates opioid receptors) and so these findings may have clinical relevance. Dr Johnson said, 'The adverse effect of antibiotics on the endorphin system may have implications not only for social behaviour but also for pain regulation. In fact we know that the gut microbiome affects the pain response so this might be one of the ways in which it does so.'

'A somewhat surprising observation from our research was the contrast in results for germ-free and antibiotic-treated mice, since the neurogenetic changes were generally in the opposite direction. This is a pertinent finding as the use of antibiotics to deplete the microbiome is often seen as a more accessible alternative to germ-free animals. However, we highlight the need to consider these two treatments as distinct models of microbiome manipulation when investigating the effects of microbes on the brain and behaviour.'

WHAT:

In a paper in the New England Journal of Medicine, scientific leaders from the National Institutes of Health set forth a framework to increase significantly the number, quality and type of daily tests for detecting SARS-CoV-2, the virus that causes COVID-19, and help reduce inequities for underserved populations that have been disproportionally affected by the disease. The authors describe the current testing landscape and explain the urgent need for nationwide deployment of low-complexity, point-of-care molecular diagnostics with rapid results. To fill this urgent need, the Rapid Acceleration of Diagnostics (RADx) program was established in just five days following the announcement of $1.5 billion in federal stimulus funding in April 2020. RADx covers the entire life cycle of the target testing technologies, is tightly focused on timelines and outcomes, receives applications from small and large companies and is expressly focused on health disparities. While based at NIH, RADx is closely coordinating with the Office of the Assistant Secretary for Health, the Biomedical Advanced Research and Development Authority, and the Department of Defense.

Current testing methods to diagnose COVID-19 detect either viral RNA or viral antigens. These tests are highly sensitive and specific when conducted in centralized laboratories with standardized protocols, but require a large amount of lab space, complex equipment, regulatory approvals for the laboratory operations and skilled technicians. Results may take hours to days, and samples often need transport to a central laboratory, furthering delays. During that time someone who is unknowingly carrying the virus may go on to infect others, instead of being quickly isolated. These issues highlight the need for reliable, rapid, point-of-care testing diagnostics.

RADx includes four major components to enable approximately 6 million daily tests in the United States by December 2020, many times the current daily testing rate. In the near term, RADx confronts the pandemic by expanding testing capacity by fall 2020 as the nation faces the beginning of seasonal flu. In the slightly longer-term RADx aims to produce additional innovative diagnostic technologies and strategies for making testing available to diverse, vulnerable and underserved populations.

* RADx tech aims to identify, accelerate development, scale up and deploy innovative point-of-care technologies throughout the fall of 2020. The program uses an "innovation funnel" design where applications quickly move through multiple stages of review with increasing scrutiny. This has been compared to a "shark tank" model. About 15-20% of RADx-tech applications will qualify for additional consideration and review. Of those applications, less than one-third will move to rigorous Phase 1 testing and validation through NIH's Point-of-care Technology Research Network (POCTRN). If a project is judged successful at that point, rapid scale up and clinical testing gets underway, with substantial financial assistance provided. As of July 13, over 600 applications had been submitted, with 27 projects advancing to Phase 1 and one project advancing to Phase 2.

* RADx Advanced Technology Platforms (RADx-ATP), will support the scale-up of more advanced technologies that can achieve immediate, substantial increases in capacity. The program uses a rapid-response application process for companies with existing point-of-care technologies authorized by the U.S. Food and Drug Administration for detecting SARS-CoV-2 that can scale production to between 20,000 and 100,000 tests per day by the fall. Additionally, RADx-ATP will seek to expand "mega-labs" across the country that can increase testing capacity to 100,000 to 250,000 tests per day.

* RADx Radical (RADx-rad) will focus on truly non-traditional approaches for testing that have a slightly longer horizon. This program will evaluate a wide range of technologies, such as home-based testing and repurposing of existing technologies for detecting SARS-CoV-2. Moreover, RADx-rad will support projects that use of biological or physiological biomarkers to detect an infection or predict the severity of disease, including the likelihood of developing multisystem inflammatory syndrome in children (MIS-C), or using chemosensory changes as an early indicator of viral positivity. Other examples include the use of biosensors to detect the presence of the virus in the breath, or the analysis of wastewater to conduct community-based surveillance.

* RADx Underserved Populations (RADx-UP) will establish community-engaged implementation projects to improve access to testing in underserved and vulnerable populations. Racial and ethnic minorities bear a higher burden of disease and mortality from COVID-19. Blacks, Latinos and American Indians/Alaska Natives are hospitalized and die at disproportionately higher rates compared to other groups. The goal of RADx-UP is to understand factors that have led to the disproportionate burden of the pandemic on underserved populations, and to support optimal access and uptake of SARS-CoV-2 testing. The program aims to examine infection patterns and efforts to increase access to and effectiveness of testing methods by building an infrastructure that can be leveraged for the ongoing COVID-19 public health efforts.

A cave deep in the wilderness of central Nevada is a repository of evidence supporting the urgent need for the Southwestern U.S. to adopt targets aimed at reducing greenhouse gas emissions, a new UNLV study finds.

UNLV climate scientist Matthew Lachniet and colleagues have compiled a detailed, 13,000-year climate history from stalagmite specimens in Leviathan Cave, located in the southern Great Basin, which provides clues for the mitigation of climate change today.

These ancient climate records show that Nevada was even hotter and drier in the past than it is today, and that one 4,000-year period in particular may represent a true, “worst-case” scenario picture for the Southwest and the Colorado River Basin — and the millions of people who rely on its water supply.

At that time, the long-term hot and dry climate of the region was linked to warm Arctic seas and a lack of sea ice, as well as warming in the western tropical Pacific Ocean, the cave record shows.

This parallels today and the near future, as the release of human carbon emissions into the atmosphere will warm the Arctic and possibly the western tropical Pacific, and is expected to result in long-term arid conditions for Nevada and the broader Colorado River Basin.

If the arid conditions become permanent, then the water supply in the Colorado River Basin is expected to decrease, which researchers say would imperil critical water resources for millions of people who live in the Southwest U.S.

“The last few decades have seen increasingly severe ‘hot droughts’ in the Colorado River Basin, when high temperatures coincide with less rainfall, and which have startled climate scientists and water policy managers,” Lachniet said. “But these dry intervals don’t usually last more than a few decades. In contrast, our new data show that Nevada climate can experience an extended interval of aridity for thousands of years, not just a few decades.”

The recent Southwestern U.S. drought that began in 2001, which has resulted in historic low reservoir levels in Lake Mead, is one indicator of the gravity of the problem. The Colorado River and Rio Grande basins are critical human support systems as their headwaters in the Rocky Mountains supply snow-fed water for myriad economic uses and support 56 million residents throughout the region.

“‘Business as usual’ scenarios for anthropogenic warming carry the risk of tipping the Southwest into an extended state of aridification,” researchers wrote.

The paper, published in the journal Paleoceanography and Paleoclimatology, provides a clearer and more comprehensive picture of the Southwest’s climate history compared to tree ring records which extend only 2,000 years into the past.

Stalagmites — like those located in Leviathan Cave — are common cave formations that act as ancient rain gauges to record historic climate data. Stalagmites grow upward at rates of inches every few hundred years as mineral-rich waters seep through the ground above and drop from the tips of stalactites on cave ceilings. 

These deposits more accurately represent a long-term shift toward a more arid climate as they hold data that extends deeper into the past.

A former analysis of one tree ring record, for example, pointed to a 10-year drought in the Medieval era as being a “worst case” predictor of a future, comparable drought, as compared to the more persistent and sustained 4,000-year period of aridity presented in Lachniet’s new study.

Regionally, paleoclimate records from other sources like lakes, landforms, pollen, and others, also support the conclusion of warmth and aridity during the same 4,000-year period.

Researchers also found that the Leviathan Cave region, where the stalagmite specimen was collected, is representative of climate conditions in most of the Mojave Desert and the southern Great Basin, and that the data has implications for the broader desert region.

Lachniet and colleagues say that their study can be a resource for policymakers today in adopting measures to reduce greenhouse gas emissions which will in turn “minimize oceanic and Arctic warming.”

“There already is evidence that droughts in the Southwest are partly caused by humans because of the higher temperatures and more evaporation in surface waters like Lake Mead,” Lachniet said. “The new fossil-fuel climate might end up making these droughts permanent.”

Journal

Paleoceanography and Paleoclimatology

DOI

10.1029/2019PA003785

Adults aged 60 and up have fared better emotionally compared to younger adults (18-39) and middle-aged adults (40-59) amid the COVID-19 pandemic, according to new UBC research published recently in the Journal of Gerontology: Psychological Sciences.

Based on daily diary data collected between mid-March and mid-April of this year, the researchers found that older adults experienced greater emotional well-being and felt less stressed and threatened by the pandemic.

"Our findings provide new evidence that older adults are emotionally resilient despite public discourse often portraying their vulnerability. We also found that younger adults are at greater risk for loneliness and psychological distress during the pandemic," says Patrick Klaiber, the study's lead author and a graduate student in the UBC department of psychology.

For the study, the researchers analyzed data from 776 participants aged 18-91, who lived in Canada and the U.S. and completed daily surveys for one week about their stressors, positive events and their emotional well-being during the first several weeks of the pandemic. The time period was selected as it was likely to be the period of greatest disruption and uncertainty as local, provincial and state governments began issuing stay-at-home orders.

Klaiber says the difference in reported stress levels may be a result of age-related stressors and how well the different age groups respond to stress.

"Younger and middle-aged adults are faced with family- and work-related challenges, such as working from home, homeschooling children and unemployment," says Klaiber. "They are also more likely to experience different types of ongoing non-pandemic stressors than older adults, such as interpersonal conflicts."

Klaiber adds, "While older adults are faced with stressors such as higher rates of disease contraction, severe complications and mortality from COVID-19, they also possess more coping skills to deal with stress as they are older and wiser."

The study also reveals older and middle-aged adults experienced more daily positive events--such as remote positive social interactions--in 75 per cent of their daily surveys, which helped increase positive emotions compared to younger adults.

"While positive events led to increases in positive emotions for all three age groups, younger adults had the least positive events but also benefited the most from them," says Klaiber. "This is a good reminder for younger adults to create more opportunities for physically-distanced or remote positive experiences as a way of mitigating distress during the pandemic."

Microplastics have been found in the guts of sharks that live near the seabed off the UK coast.

University of Exeter scientists studied four species of demersal (seabed-dwelling) shark.

Of the 46 sharks examined, 67% contained microplastics and other man-made fibres.

A total of 379 particles were found and - though the impact on the sharks' health is unknown - the researchers say it highlights the "pervasive nature of plastic pollution".

"Our study presents the first evidence of microplastics and anthropogenic fibre contaminants in a range of native UK demersal shark species," said lead author Kristian Parton, of the Centre for Ecology and Conservation at Exeter's Penryn Campus in Cornwall.

Commenting on the possible sources of the particles, he added: "We were surprised to find not only microplastics but also particles such as synthetic cellulose, which is most commonly found in textiles (including disposable hygiene items like facemasks) and clothing.

"When clothes are washed, or items are discarded as litter, tiny fibres are released and these often flow into water sources and out to sea.

"Once in the sea, microfibres can either float or sink to the bottom, which is where these sharks live.

"The fibres could then be ingested via the sharks' food, which is mostly crustaceans, or directly through the sediment on the seabed.

"In terms of the other types of microplastics we found, many of these may have come from fishing lines or nets."

The research team, which included scientists from Greenpeace Research Laboratories, examined the stomachs and digestive tracts of four species: small-spotted catshark, starry smooth-hound, spiny dogfish and bull huss.

These species can be found at varying depths from 5-900m, but usually live and feed near the sea floor.

Though the study is based on a modest sample size, the findings suggest larger sharks contained more particles. No differences were found based on sex or species.

The study was conducted in Cornwall, UK, using sharks caught as "bycatch" (by accident) in a demersal hake fishery, fishing in and around the North-East Atlantic and Celtic Sea.

Study co-author Professor Tamara Galloway, of Exeter's Global Systems Institute, said: "We were not expecting to find microfibres from textiles in so many of our native shark species.

"Our study highlights how important it is to think before we throw things away."

Dr Laura Foster, Head of Clean Seas at the Marine Conservation Society, added: "The new research from into these iconic shark species around the UK shows high levels of microplastic ingestion, with 95% of the contaminants found being fibrous."

WASHINGTON - (July 22, 2020) - A mouse model of glioblastoma, an aggressive type of cancer that can occur in the brain, suggests that this recalcitrant cancer originates from a pool of stem cells that can be a significant distance away from the resulting tumors. The findings of a new study, led by Children's National Hospital researchers and published July 22 in the journal Nature Communications, suggest new ways to fight this deadly disease.

Despite decades of research, glioblastoma remains the most common and lethal primary brain tumor in adults, with a median survival of only 15 months from diagnosis, says study leader Yuan Zhu, Ph.D., the scientific director and endowed professor of the Gilbert Family Neurofibromatosis Institute at Children's National. Unlike many cancers, which start out as low-grade tumors that are more treatable when they're caught at an early stage, most glioblastomas are almost universally discovered as high-grade and aggressive lesions that are difficult to treat with the currently available modalities, including surgery, radiation and chemotherapy.

"Once the patient has neurological symptoms like headache, nausea, and vomiting, the tumor is already at an end state, and disease progression is very rapid," Dr. Zhu says. "We know that the earlier you catch and treat cancers, the better the prognosis will be. But here, there's no way to catch the disease early."

However, some recent research in glioblastoma patients shows that the subventricular zone (SVZ) -- an area that serves as the largest source of stem cells in the adult brain -- contains cells with cancer-driving mutations that are shared with tumors found in other often far-distant brain regions.

To see if the SVZ might be the source for glioblastoma tumors, Dr. Zhu and his colleagues worked with mouse models that carried a single genetic glitch: a mutation in a gene known as p53 that typically suppresses tumors. Mutations in p53 are known to be involved in glioblastoma and many other forms of cancer.

Starting from about 5.5 months old, these animals received weekly brain scans to look for tumors that arise when the stem cells subsequently acquire more mutations. Those mice that developed brain tumors fell into two categories. While about 30% developed a single mass that appeared at a high grade, the majority of these animals developed high-grade tumors at multiple spatially segregated areas.

Using genetic tests and an approach akin to those used to study evolution, the researchers traced the cells that spurred both kinds of tumors back to the SVZ. Although both single and multiple tumors had spontaneously acquired mutations in a gene called Pten, another type of tumor suppressor, precursor cells for the single tumors appeared to acquire this mutation before they left the SVZ, while precursor cells for the multiple tumors developed this mutation after they left the stem cell niche. When the researchers genetically altered the animals to shut down the molecular pathway that loss of Pten activates, it didn't stop cancer cells from forming. However, rather than migrate to distal areas of the brain, these malignant cells remained in the SVZ.

Dr. Zhu notes that these findings could help explain why glioblastoma is so difficult to identify the early precursor lesions and treat. This work may offer potential new options for attacking this cancer. If new glioblastoma tumors are seeded by cells from a repository in the SVZ, he explains, attacking those tumors won't be enough to eradicate the cancer. Instead, new treatments might focus on this stem cell niche as target for treatment or even a zone for surveillance to prevent glioblastoma from developing in the first place.

Another option might be to silence the Pten-suppressed pathway through drugs, a strategy that's currently being explored in various clinical trials. Although these agents haven't shown yet that they can stop or reverse glioblastomas, they might be used to contain cancers in the SVZ as this strategy did in the mouse model -- a single location that might be easier to attack than tumors in multiple locations.

"The more we continue to learn about glioblastoma," Dr. Zhu says, "the more hope we can give to these patients who currently have few effective options."

Scientists can now explain how baby reef sharks tolerate living in the sometimes-extreme environments of their nurseries--but, they also say these habitats face an uncertain future which may leave newborn sharks 'trapped'.

The lead author of the study is Ian Bouyoucos, a PhD student at the ARC Centre of Excellence for Coral Reef Studies at James Cook University (Coral CoE at JCU).

"Nearshore, shallow water nurseries provide food and abundant shelter where baby blacktip reef sharks can avoid bigger predators, such as other sharks," Mr Bouyoucos said.

Though the word 'nursery' conjures images of soft, nurturing environments, these shallows are anything but. The habitats can be 'extreme', with dramatic changes in temperature and oxygen levels.

"It's not a nice place really, in terms of environmental conditions," said co-author Associate Professor Jodie Rummer, also from Coral CoE at JCU. The extremes of the shallows can mean high temperatures and low oxygen levels, which can be a strain at best.

"But we found the growth rate and metabolism of baby sharks is resilient to the temperature changes they currently face in these shallow habitats," Mr Bouyoucos said.

"We also found the sharks with a greater tolerance for higher temperatures had a greater tolerance for low oxygen levels, which is really promising."

Dr Rummer said mother blacktip reef sharks usually give birth close to shore. There may be, at most, only four pups born at a time with perhaps only one surviving.

"Essentially from the day they are born, these sharks have to be pretty tough in how their bodies work in order to tolerate these harsh environmental conditions," Dr Rummer said.

The research was conducted within the largest shark sanctuary in the world--the French Polynesian shark sanctuary. The top threat to sharks worldwide is overfishing, but sharks are protected within the 4.8 million square kilometre sanctuary.

Though the young sharks appear resistant to extreme changes the authors warn, as waters get warmer with climate change, future populations are threatened. While the sanctuaries might successfully remove the number one threat to these sharks, they don't protect against their second biggest threat: climate change.

"We know that healthy ocean ecosystems need healthy predators, and that healthy predators need healthy ecosystems--you can't have one without the other," Dr Rummer said.

She says newborn sharks have a narrow window of time in nursery habitats, where they have to grow, learn to hunt, and not get eaten.

"So, if these ecosystems disintegrate under climate change, the baby sharks fall into a 'trap'," Dr Rummer said.

"If they choose less harsh habitats, they lose their food and protection. If they remain within the safe, shallow nurseries, they suffer the effects of warming waters and decreasing oxygen levels. A trap, indeed."

Mr Bouyoucos says while these sharks can cope with these challenging conditions now, they are approaching their limits.

"There are already extreme fluctuations and extreme highs going on in the shallows--and the conditions are only getting worse," he said.

"We have to ask, will reef sharks continue to adapt and evolve over generations at a pace that's fast enough to keep up with climate change?"

Scientists at the U.S. Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL) have furthered understanding of a barrier that can prevent doughnut-shaped fusion facilities known as tokamaks from operating at high efficiency by causing vital heat to be lost from them.

Led by PPPL physicist Roscoe White, the research team used computers to simulate a type of plasma movement that can bump highly energetic particles from the core to the edge, a phenomenon that could occur in ITER, the multinational tokamak being built in France to demonstrate the feasibility of fusion as an energy source.

"For any fusion device to work, you need to make sure that the highly energetic particles within it are very well confined within the plasma core," said PPPL physicist Vinícius Duarte, a member of the research team that reported the results in Physics of Plasmas. "If those particles drift to the edge of the plasma, you can't sustain the steady-state burning plasma needed to make fusion-powered electricity a reality."

Duarte refers to a phenomenon called "chirping" that occurs when the frequency of the waves of plasma that interact with highly energetic particles changes suddenly, ultimately causing energy to escape from the plasma core and produce rapidly changing tones. The new findings, which elucidate aspects of how chirping forms in a tokamak, could help researchers figure out how to thwart the chirps and keep in the vital heat. Preventing the sudden frequency changes could also protect the tokamak walls from the sudden release of concentrated and damaging bursts of energy.

Fusion combines light elements in the form of plasma -- the hot, charged state of matter composed of free electrons and atomic nuclei -- and generates massive amounts of energy in the stars. Scientists aim to replicate fusion in devices on Earth for a virtually inexhaustible supply of safe and clean power to generate electricity.

The researchers used computer simulations showing highly detailed views of the movement of plasma particle conglomerations to reveal some of the mechanisms responsible for chirping, giving hope that scientists can find ways to ameliorate its effects. Scientists used the PPPL code ORBIT to calculate how the position and velocity of plasma particles change over time in three dimensions. The simulations showed that chirping begins when fast-moving particles in the core interact with waves undulating through the plasma and spontaneously form clumps that migrate to the plasma edge. The findings confirm earlier results based on simplified tokamak configurations; they also reveal richer and more complex dynamics not seen before.

This interaction with plasma particles causes the frequency of the so-called plasma Alfvén waves to simultaneously rise and drop, catapulting the clumps out toward the plasma edge and sometimes into the wall. "The tools developed in this research have enabled a glimpse into the complicated, self-organized dynamics of the chirps in a tokamak," Duarte said.

The scientists had to create new virtual tools to observe the movement of the simulated waves with the needed detail. "The hardest thing was inventing the diagnostics that would cleanly show what was going on," said White. "In a certain sense, it's like building a microscope that will let you view what you need to view."

The new findings continue a long-standing effort by members of the PPPL Theory Department that focuses on understanding chirping, especially within PPPL's National Spherical Tokamak Experiment-Upgrade (NSTX-U). "If you understand it," says White, "you can find ways to operate fusion facilities without it."

What The Study Did: This study estimates how common SARS-CoV-2 antibodies are in convenience samples from 10 geographic sites in the United States.

Authors: Fiona P. Havers, M.D., M.H.S., of the CDC COVID-19 Response Team at the Centers for Disease Control and Prevention in Atlanta, 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/jamainternmed.2020.4130)

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

Surface plasmons in graphene have been widely studied in the past decade due to their very appealing properties, such as the strong tunability of its optical properties through electrical gating and the relatively high plasmon lifetime. However, these exceptional properties are limited to lower frequencies ranging from the mid-infrared (mid-IR) to the terahertz (THz) spectral regions. Additionally, electrical tunability of graphene cannot be achieved in an ultrafast manner, what poses an obstacle for its application in high-speed technological devices that are becoming increasingly important.

In a new paper published in Light Science & Application, a team from ICFO-Institut de Ciencies Fotoniques (Barcelona, Spain) has proposed an all-optical technique to modulate the plasmonic response of graphene- and/or thin-metal-based systems in an ultrafast manner, in a spectrum ranging from mid-infrared to visible (vis-NIR) frequencies. They propose a pump-probe setup where an ultrafast and very intense pump beam is used to heat the electrons of the graphene. Based on the low heat capacity of this 2D material -meaning that a small amount of energy absorbed by this material can induce a large increase in the temperature of its electrons- and on the strong dependence of graphene's conductivity with its electronic temperature, the optical properties of the system will be modulated by the electronic temperature increase, and this can be measured by the probe beam.

Interestingly, this technique can be used to all-optically excite plasmons not only in the graphene sheet, but also in a thin metallic layer placed nearby it. Following a previous work by the same group, they propose to do so by engineering a pump beam such that its wave-front intensity varies spatially in a periodic manner. As such, the electronic temperature in graphene (and subsequently its conductivity) also varies locally in the surface of the sheet, acting as an effective grating that scatters the probe beam and couples it into plasmons. Depending on the wavelength of the probe beam and the presence of a metallic thin film nearby the graphene sheet, this technique can be used to excite either graphene plasmons (mid-IR), metallic plasmons (vis-NIR) or hybrid acoustic plasmons (THz). "In this way, one can excite and manipulate plasmons in a wide spectral range without the need for lateral patterning or using external devices, like SNOM tips, to couple propagating light into plasmons" the authors added.

On a different note, the authors propose to employ nanoscale photothermal effects in order to achieve ultrafast modulation of light. They envision a structure composed of a thin metallic grating on top of a graphene sheet doped to some Fermi level. Then, by increasing the temperature of the graphene electrons via a pump beam, the chemical potential of graphene will decrease, and the interband transitions in graphene will become significant at lower energies, and will quench the plasmonic peak measured by the reflection of a probe beam. "The temperature of graphene electrons can achieve several thousands of Kelvins, resulting in a damping of the reflection peak up to 70%", the authors claim. A similar effect can be observed in graphene acoustic plasmons, but in this case the reason for the quenching is the increasing of the graphene inelastic losses with the electronic temperature. "In both cases, the modulation of the optical response is ultrafast, unlike alternative ways to modulate the response, such as electrically changing the Fermi level of graphene", the authors added.

"Our study opens a promising avenue toward the active photothermal manipulation of the optical response in atomically thin materials with potential applications in ultrafast light modulation", the authors conclude.

A field studying something very small is becoming very big: In the last decade, the field of nanoparticle research has exploded. At about one nanometer in size, nanoparticles are 100,000 times smaller than the width a strand of human hair and cannot be seen with the naked eye, but researchers are discovering broad uses for them in fields ranging from bioimaging to energy and the environment.

Working at this scale, it is difficult to be precise; however, the Computer-Aided Nano and Energy Lab (CANELa) at the University of Pittsburgh's Swanson School of Engineering is advancing the field, modeling metal nanoclusters that are atomically precise in structure. An article highlighting their work and its influence on the field of nanoparticles is featured on the cover of the latest issue of Dalton Transactions.

"One major benefit of these very small systems is that by knowing their exact structure, we can apply very accurate theory," said Giannis "Yanni" Mpourmpakis, Bicentennial Alumni Faculty Fellow and associate professor of chemical engineering, who leads the CANELa. "With theory we can then investigate how properties of nanoclusters depend on their structure."

Ligand-protected metal nanoclusters are a unique class of nanomaterials that are sometimes referred to as "magic size" nanoclusters because of their high stability when they have specific compositions. One of the key advances their lab has made to the field, with funding from the National Science Foundation, is in modeling the specific number of gold atoms stabilized by a specific number of ligands, on the surface.

"With larger nanoparticles, researchers may have an estimate of how many atoms exist on each structure, but our modelling of these nanoclusters is exact. We can write out the precise molecular formula," explained Michael Cowan, graduate student in the CANELa and lead author on the article. "If you know the exact structure of small systems you can tailor them to create active sites for catalysis, which is what our lab focuses on most."

Predicting new alloys and previously undiscovered magic sizes is the next step that the field--and the lab--will need to tackle. The lab uses computational chemistry methods to model known nanoclusters, but creating a complete database of nanocluster structure, property and synthesis parameters will be the next step to apply machine learning and create a prediction framework.

NASA-NOAA's Suomi NPP satellite passed over the Eastern Pacific Ocean and provided forecasters with a visible image of the waning Tropical Depression 7E. Wind shear and cooler waters were taking their toll on the storm.

The Visible Infrared Imaging Radiometer Suite (VIIRS) instrument aboard Suomi NPP provided a visible image of the storm on Monday, July 20 at 6:36 p.m. EDT (2236 UTC) and revealed it was devoid of strong thunderstorms. The VIIRS image showed that the only deep convection associated with the depression was a small shapeless patch of clouds pushed about 70 miles to the west of the poorly defined surface center of circulation.

Vertical wind shear, that is, winds outside of a tropical cyclone at different heights in the atmosphere (the troposphere), pushes against a tropical cyclone and tears it apart. Tropical Depression 7E is being battered by easterly winds. The system is also moving over waters too cool to maintain strength. Tropical cyclones need sea surface temperatures of at least 26.6 degrees Celsius (80 degrees Fahrenheit) and 7E is moving through waters as cool as 24 to 25 degrees Celsius (75.2 to 77 degrees Fahrenheit).

At 5 a.m. EDT (0900 UTC) on July 22, the National Hurricane Center (NHC) found center of Tropical Depression 7E near latitude 19.3 degrees north and longitude 133.0 degrees west. That is about 1,505 miles (2,425 km) west of the southern tip of Baja California, Mexico. The depression was moving toward the west near 13 mph (20 kph), and this general motion is expected to continue for the next day or so. Maximum sustained winds are near 35 mph (55 kph) with higher gusts.

At that time, NHC said, "The system is forecast to become a remnant low within the next few hours. The winds associated with the remnant low should gradually diminish during the next day or two until the system dissipates."

Satellite imagery on July 22 revealed that 7E does not have any strong thunderstorms, and is now devoid of all deep convection. If deep convection does not redevelop soon, it will become a remnant low early Tuesday.

Tropical cyclones/hurricanes are the most powerful weather events on Earth. NASA's expertise in space and scientific exploration contributes to essential services provided to the American people by other federal agencies, such as hurricane weather forecasting.

For updated forecasts from the NHC, visit: http://www.nhc.noaa.gov

INDIANAPOLIS -- The results of the first statewide random sample study in the United States to measure the spread of COVID-19 indicated a general population prevalence of about 2.8 percent in Indiana.

This closely monitored study was conducted by the Indiana University Richard M. Fairbanks School of Public Health at IUPUI in collaboration with the Indiana State Department of Health. The findings were published July 21 in Morbidity and Mortality Weekly Report, the U.S. Centers for Disease Control and Prevention's scientific publication.

"Using data to guide decisions has been the foundation of how the State of Indiana responds to the pandemic," Indiana Gov. Eric J. Holcomb said. "We are fortunate to have the Fairbanks School of Public Health conduct this first-of-its kind study for us and look forward to the information that will come with future waves of the random sample testing."

Between April 25 and May 1, researchers tested more than 4,600 Hoosiers for viral infections and antibodies of SARS-CoV-2, the novel coronavirus that causes COVID-19. This number includes more than 3,600 people who were randomly selected from a master list of Indiana residents derived from tax returns, including filers and dependents; and an additional 900 volunteers recruited through nonrandom outreach to the African American and Hispanic communities to get a more in-depth view of the virus's activity within hard-hit populations.

"Because we cannot test everyone, random sample testing allows us to confidently evaluate the spread of COVID-19 in Indiana," said Nir Menachemi, lead scientist on the study and professor and Fairbanks Endowed Chair in the Fairbanks School of Public Health. "The results of this study have furthered our scientific knowledge of COVID-19 and contributed valuable information that influenced complex statewide decision-making."

The researchers determined that 1.7 percent of participants tested positive for the novel coronavirus and an additional 1.1 percent tested positive for antibodies, resulting in an estimated overall population prevalence of SARS-CoV-2 of 2.8 percent. An estimated 187,802 Hoosiers were infected with COVID-19 at the time of the study, approximately 10 times higher than the confirmed cases in the state.

Participants who reported living with someone who tested positive for COVID-19 had a prevalence rate of 33.6 percent.

"The percentage of participants who had a positive test result was 15 times higher among participants who lived with someone who had received a diagnosis of COVID-19," Menachemi said. "Coupled with the low statewide prevalence, we believe that social distancing efforts helped to minimize the spread of COVID-19 and is an important measure in preventing transmission."

The research team also found that 44.2 percent of participants who tested positive reported no symptoms during the two weeks before testing. Of those who tested positive, 60.3 percent of males reported being asymptomatic, compared to 24.5 of females who were asymptomatic.

"The study's findings among asymptomatic individuals are crucial to our efforts to mitigate the spread of COVID-19 in Indiana," said State Health Commissioner Kris Box, M.D., FACOG. "Hoosiers may not feel sick but can still infect someone else, so it's vital that every Hoosier takes steps to reduce the spread of this virus."

Rates of current or previous infection were significantly higher among Hispanic participants, at 8.32 percent, than among non-Hispanics, at 2.29 percent.

The nonrandom sample had higher infection rates, including 22.8 percent of participants who were currently infected; 20 percent of those infected reported being asymptomatic. These findings suggest that nonrandom samples are more suitable for determining the impact of the virus in vulnerable communities, but not for deriving state estimates of infections.

"Because most Hoosiers had not been infected at the time of the study, we need to continue social distancing, make sure we are washing our hands often and always wearing a mask when we are in public," Menachemi said.