The paper is published in the journal Atmospheric Chemistry and Physics.

The research team, led by Joannes Maasakkers, a former graduate student at SEAS, developed a method to trace and map total emissions from satellite data to their source on the ground.

“This is the first country-wide evaluation of the emissions that the EPA reports to the United Nations Framework Convention on Climate Change (UNFCC),” said Maasakkers, who is currently a scientist at the SRON Netherlands Institute for Space Research.

Currently, the EPA only reports total national emissions to the UNFCC. In previous research, Maasakkers and his collaborators, including Daniel Jacob, the Vasco McCoy Family Professor of Atmospheric Chemistry and Environmental Engineering at SEAS, worked with the EPA to map regional emissions of methane from different sources in the US. That level of detail was used to simulate how methane moves through the atmosphere.

In this paper, the researchers compared those simulations to satellite observations from 2010-2015. Using a transport model, they were able to trace the path of emissions from the atmosphere back to the ground and identify areas across the US where the observations and simulations didn’t match up.

“When we look at emissions from space, we can only see how total emissions from an area should be scaled up or down, but we don’t know the source responsible for those emissions,” said Maasakkers. “Because we spent so much time with the EPA figuring out where these different emissions occur, we could use our transport model to go back and figure out what sources are responsible for those under- or over-estimations in the national total.”

The biggest discrepancy was in emissions from oil and natural gas production.

The EPA calculates emission based on processes and equipment. For example, the EPA estimates that a gas pump emits a certain amount of methane, multiplies that by how many pumps are operating across the country, and estimates total emissions from gas pumps.

“That method makes it really hard to get estimates for individual facilities because it is hard to take into account every possible source of emission,” said Maasakkers. “We know that a relatively small number of facilities make up most of the emissions and so there are clearly facilities that are producing more emissions than we would expect from these overall estimates.”

The researchers hope that future work will provide more clarity on exactly where these emissions are coming from and how they are changing.

“We plan to continue to monitor U.S. emissions of methane using new high-resolution satellite observations, and to work with the EPA to improve emission inventories,” said Jacob.

“It’s important to understand these emissions better but we shouldn’t wait until we fully understand these emissions to start trying to reduce them,” said Maasakkers. “There are already a lot of things that we know we can do to reduce emissions.”

This paper was co-authored by Daniel Jacob, Melissa Sulprizio, Tia R. Scarpelli, Hannah Nesser, Jianxiong Sheng, Yuzhong Zhang, Xiao Lu, A. Anthony Bloom, Kevin Bowman, John Worden, and Robert Parker.

The research was funded by the NASA Carbon Monitoring System (CMS) program.

“We found that the large spin-orbit coupling and strong electronic correlations in a system of uranium-cobalt-aluminum doped with ruthenium resulted in a colossal anomalous Nernst conductivity,” said Filip Ronning, lead investigator on the paper published today in Science Advances. Ronning is director of the Institute for Materials Science at Los Alamos National Laboratory. “It illustrates that uranium and actinide alloys are promising materials to study the interplay among a material’s topology and strong electron correlations. We’re very much interested in understanding, tuning and eventually controlling this interplay, so hopefully one day we can exploit some of these remarkable responses.”

The Nernst response occurs when a material converts a flow of heat into an electric voltage. This thermoelectric phenomenon can be exploited in devices that generate electricity from a heat source. The most notable current example is the radioisotope thermoelectric generators (RTGs) that were developed in part at Los Alamos. RTGs use heat from the natural radioactive decay of plutonium-238 to generate electricity — one such RTG is currently powering the Perseverance rover on Mars.

“What’s exciting is that this colossal anomalous Nernst effect appears to be due to the rich topology of the material. This topology is created by a large spin-orbit coupling, which is common in actinides,” Ronning said. “One consequence of topology in metals is the generation of a transverse velocity, which can give rise to a Nernst response as we observe. It can also generate other effects such as novel surface states that may be useful in various quantum information technologies.”

The uranium system studied by the Los Alamos team generated 23 microvolts per kelvin of temperature change — four times bigger than the previous record, which was discovered in a cobalt-manganese-gallium alloy a couple of years ago and also attributed to these sorts of topological origins.

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The team studied fruit flies and cutting-edge brain cell models called organoids. They focused on the signals muscles send when stressed. The researchers found that stress signals rely on an enzyme called Amyrel amylase and its product, the disaccharide maltose.

The scientists showed that mimicking the stress signals can protect the brain and retina from aging. The signals work by preventing the buildup of misfolded protein aggregates. Findings suggest that tailoring this signaling may potentially help combat neurodegenerative conditions like age-related dementia and Alzheimer’s disease.

“We found that a stress response induced in muscle could impact not only the muscle but also promote protein quality control in distant tissues like the brain and retina,” said Fabio Demontis, PhD, of St. Jude Developmental Neurobiology. “This stress response was actually protecting those tissues during aging.”

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“The demonstration of high single-photon purity in the infrared has immediate utility in areas such as quantum key distribution for secure communication,” said Victor Klimov, lead author of a paper published today in Nature Nanotechnology by Los Alamos National Laboratory scientists.

The Los Alamos team has developed an elegant approach to synthesizing the colloidal-nanoparticle structures derived from their prior work on visible light emitters based on a core of cadmium selenide encased in a cadmium sulfide shell. By inserting a mercury sulfide interlayer at the core/shell interface, the team turned the quantum dots into highly efficient emitters of infrared light that can be tuned to a specific wavelength.

“This new synthesis allows for highly accurate, atomic-level control of the thickness of the emitting mercury sulfide interlayer. By changing it in increments of a single atomic layer, we can tune the wavelength of the emitted light in discrete quantized jumps, and further adjust it in a more continuous fashion by tuning the cadmium selenide core size,” said Vladimir Sayevich, the lead chemist on this project.

Far superior to existing near-infrared quantum dots, these new structures show “blinking-free” emission at a single-dot level, nearly perfect single-photon purity at room temperature (which produces “quantum light”), and fast emission rates. They behave extremely well with both optical and electrical excitation.

Single photons can be used as qubits in quantum computing. In a cybersecurity application, single photons can protect a computer network through quantum key distribution, which provides ultimate security through “unbreakable” quantum protocols.

Bio-imaging is another important application. The emission wavelength of the newly developed quantum dots is within the near-infrared bio-transparency window, which makes them well suited for deep tissue imaging.

People can’t see infrared light, but many modern technologies rely on it, from night-vision devices and remote sensing to telecommunications and biomedical imaging. Infrared light is also a big player in emerging quantum technologies that rely on the duality of light particles, or photons, which can also behave as waves. Exploiting this quantum property requires sources of “quantum light” that emit light in the form of individual quanta, or photons.

“There is also a cool chemical element in achieving single-atomic layer accuracy in making these dots,” said Zack Robinson, the project member focusing on quantum dot spectroscopy. “The thickness of the emitting mercury sulfide interlayer is identical across all dots in the samples. That’s very unique, especially for a material made chemically in a beaker.”

Klimov added, “However, this is just the first step. In order to take full advantage of ‘quantum light’ one needs to achieve photon indistinguishability, that is, to make sure that all emitted photons are quantum-mechanically identical. This is an extremely difficult task, which we will tackle next in our project.”

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The novel active ingredient is a so-called aptamer. These are short chains of DNA, the chemical compound that also makes up chromosomes. DNA chains like to attach themselves to other molecules; one might call them sticky. In chromosomes, DNA is therefore present as two parallel strands whose sticky sides face each other and that coil around each other like two twisted threads.

Aptamers, on the other hand, are single-stranded. This allows them to form bonds with molecules to which conventional DNA would not normally bind and to influence their function. This makes them interesting for research into active ingredients, especially since it is now very easy to produce huge libraries of different aptamers. Some of these libraries contain millions of times more potential active ingredients than there are people living on Earth. “We used such a library to isolate aptamers that can attach to the spike protein of SARS coronavirus 2,” explains Prof. Dr. Günter Mayer of the LIMES Institute (the acronym stands for “Life and Medical Sciences”) at the University of Bonn.

Spike is essential for the infection

The spike protein is essential for the virus: It uses it to dock onto the cells it attacks. In the process, the protein binds to a molecule on the surface of its victims called ACE2, which effectively locks into the spike protein, much like a ski boot in a ski binding. The virus then fuses with the cell and reprograms it to produce numerous new viruses. “The vast majority of antibodies we know today prevent docking,” Mayer explains. “They attach to the part of the spike protein responsible for recognizing ACE2, which is the receptor binding domain, or RBD.”

The now isolated aptamer with the abbreviation SP6 also binds to the spike protein, but at a different site. “SP6 does not prevent viruses from docking to target cells,” explains Prof. Dr. Michael Famulok of the LIMES Institute, who also works at the caesar research center in Bonn. “Nevertheless, it reduces the level of cell infection by the virus; we do not yet know which mechanism is responsible for this.” The researchers did not use real coronaviruses in their experiments, but so-called pseudoviruses. These carry the spike protein on their surface; however, they cannot cause disease. “We now need to see if our results are confirmed in real viruses,” Famulok therefore emphasizes.

New Achilles heel of coronavirus?

If so, in the medium term the work could for instance result in a kind of nasal spray that protects against coronavirus infection for a few hours. The necessary studies will certainly take months to complete. Irrespective of this, however, the results may help to better understand the mechanisms involved in infection. This is all the more important because the existing active ingredients mainly target the receptor domain. In the so-called “British mutation,” this domain is altered so that it binds more strongly to ACE2. “The more such mutations accumulate, the greater the risk that the available drugs and vaccines will no longer work,” stresses Günter Mayer. “Our study may draw attention to an alternative Achilles’ heel of the virus.”

The results are also evidence of successful cooperation: Mayer and his postdoctoral researcher Dr. Anna Maria Weber were primarily responsible for characterizing the aptamer. Prof. Famulok’s group at the caesar research center was responsible for conducting the pseudovirus experiments, which were led by his colleague Dr. Anton Schmitz. Famulok and Mayer are members of the Transdisciplinary Research Areas “Life & Health” and “Building Blocks of Matter and Fundamental Interactions.” Mayer also heads the Center of Aptamer Research and Development (CARD) at the University of Bonn.

The study was funded by the German Federal Ministry of Education and Research (BMBF) and the German Research Foundation (DFG).

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“We are looking at water scarcity as a globally connected and multi-sector phenomenon,” said Jonathan Lamontagne, assistant professor of civil and environmental engineering at Tufts University, who co-authored the study with Patrick Reed, the Joseph C. Ford Professor of Civil and Environmental Engineering at Cornell. Tufts graduate student Flannery Dolan is lead author of the study, which suggests water scarcity dynamics are more complicated than traditionally acknowledged.

The study, “Evaluating the economic impact of water scarcity in a changing world,” was published March 26 in Nature Communications, and uniquely captures the interdependent effects of global trade consistently with differences in regional climate policies as well as river basin-specific capacity to address water scarcity risks.

The researchers coupled physical and economic models to simulate thousands of potential climate futures for 235 major river basins — a technique known as scenario discovery — to better understand how water scarcity is a globally-connected phenomenon, with local conditions having reverberations across the globe in industries such as agriculture, energy, transportation and manufacturing.

The research found that global trade dynamics and market adaptations to regional water scarcity result in positive and negative economic outcomes for every regional river basin considered in the study.

For instance, in the lower Colorado River basin, the worst economic outcomes arise from limited groundwater availability and high population growth, but that high population growth can also prove beneficial under some climatic scenarios. In contrast, the future economic outcomes in the Indus Basin depend largely on global land-use policies.

“What is happening elsewhere in the world through differences in regional choices related to energy transitions — how land is being managed as well as different regional water demands and adaptive choices — can shape relative advantages and disadvantages of water intensive economic activities,” said Reed.

Restrictions in water availability usually lead to a negative regional economic impact, but the research revealed that some regions can experience a positive economic impact if they hold an advantage over other water basins and can become a virtual exporter of water. The Orinoco basin in Venezuela, for example, usually has a reliable supply of water and is often in a relative position that can benefit when other regions are under stress, according to the researchers.

The study also found that small differences in projections for future climate conditions can yield very large differences in the economic outcomes for water scarcity.

“Human activities and market responses can strongly amplify the economic effects of water scarcity, but the conditions that lead to this amplification vary widely from one basin to the next,” said Lamontagne.

A river basin can be considered economically robust if it is able to adapt to drought with alternative sources of water or adjust economic activity to limit usage. If a basin is unable to adapt its supply options and if prolonged water scarcity leads to persistent economic decline, then the researchers describe the loss in water basin adaptive capacity as having reached an ‘economic tipping point.’

For example, in the Indus region in South Asia, the water supply is under stress due to heavy agricultural use and irrigation leading to unsustainable consumption of groundwater, which places it close to the tipping point.

The conditions that lead to these tipping points are highly variable from basin to basin, depending on a combination of local factors and global conditions. In the Arabian Peninsula, low groundwater availability and pricing of carbon emissions are key factors. In the lower Colorado River basin, a mixture of low groundwater availability, low agricultural productivity, and strong economic demands from the U.S. and Europe lead to tipping points.

“It is noteworthy that the lower Colorado River basin has some of the most uncertain and widely divergent economic outcomes of water scarcity of the basins analyzed in this study,” said Reed. “This implies that assumed differences in regional, national and global human system conditions as well as the intensity of climate change can dramatically amplify the uncertainty in the basin’s outcomes.”

As climate change makes the physical and economic effects of water scarcity more challenging for policy makers to understand, the researchers hope their work will provide the basis for similar analyses and draw attention to the importance of expanded data collection to improve modeling and decision making.

The study was co-authored by researchers from the Joint Global Change Research Institute at the Pacific Northwest National Laboratory, and was supported by the U.S. Department of Energy’s Office of Science.