A key brain region for substance use disorders now has a searchable atlas of distinct cell populations

In a work of systematic biology that advances the field, University of Alabama at Birmingham researchers have identified 16 distinct cell populations in a complex area of the midbrain called the ventral tegmental area, or VTA.

The VTA is important for its role in the dopamine neurotransmission involved in reward-directed behavior. Substance use disorders involve dysregulation of these reward circuits, leading to repeated drug-seeking despite adverse consequences. These include more than 100,000 drug overdose deaths in the United States in the most recent year. The VTA also has a role in several other neuropsychiatric disorders.

Thus, expanding knowledge of its function is a start to explaining the mechanisms for substance use disorders involving drugs like cocaine, alcohol, opioids and nicotine, or psychiatric disorders like schizophrenia and attention deficit hyperactivity, or ADHD.

Dopamine is one of the neurotransmitters used by the brain as chemical messengers to send signals between nerve cells. While decades of research have focused on dopaminergic neurotransmission in the VTA, there is also substantial evidence for the importance of two other neurotransmitters acting in the VTA in reward-related behaviors — GABA and glutamate. There is also evidence for “combinatorial” neurons that can potentially synthesize and release multiple neurotransmitters. These suggest an additional layer of complexity in VTA cellular and synaptic function.

Systematic biology is the science of classification, and it usually refers to the classification of organisms with regard to their natural relationships. The UAB VTA study classifies cell populations to extend and deepen previous work on the different cell types in the VTA, to provide a starting point for deciphering the relationships among these cells and their broad connections to other areas of the brain. The research, published in Cell Reports, was led by co-first authors Robert A. Phillips III and Jennifer J. Tuscher, Ph.D., and corresponding author Jeremy J. Day, Ph.D.

The 16 distinct cell populations were identified by differences in gene expression after single-nucleus RNA sequencing of 21,600 cells from the rat VTA, creating a searchable online atlas of the VTA. The rat is the prime model for reward and substance use studies. This unbiased approach — in contrast to previous studies that selected some subsets of cells for RNA sequencing — was used to create the largest and most comprehensive single-cell transcriptomic analysis focused exclusively on the composition and molecular architecture of the VTA.

Though it was well known that the VTA is composed of heterogeneous cell types, the UAB atlas expands those studies in several key ways.

“For example, previous single-cell sequencing studies were conducted exclusively in the mouse brain and have relied primarily on sequencing a subset of fluorescence-activated cell sorting-isolated midbrain dopaminergic populations, rather than sampling all VTA cell types,” Day said. “Notably, our sequencing dataset focuses exclusively on VTA sub-regions, unlike other studies that have focused on pooled cells from the mouse substantia nigra and VTA or a subset of fluorescently tagged cells from general midbrain regions.”

The 16 distinct cell populations include classic dopaminergic neurons, three subsets of glutamatergic neurons and three subsets of GABAergic neurons, as well as nine other cell types, including astrocytes and glial cells.

After sub-clustering neuronal cells, the UAB researchers also identified four sub-clusters that may represent neurons capable of combinatorial neurotransmitter release. They also identified selective gene markers for classically defined dopamine neurons and for the combinatorial neurons. A selective marker allows viral targeting of distinct VTA subclasses for functional studies.

The researchers also examined sub-clusters for opioid neuropeptides and their receptors, and identified pan-neuronal increased expression for risk genes associated with schizophrenia and “smoking initiation,” as well as enrichment of ADHD risk genes in two glutamatergic neuronal populations.

Co-authors besides Day, Phillips and Tuscher for the study, “An atlas of transcriptionally defined cell populations in the rat ventral tegmental area,” are Samantha L. Black, Emma Andraka and N. Dalton Fitzgerald, UAB Department of Neurobiology and Evelyn F. McKnight Brain Institute; and Lara Ianov, Civitan International Research Center at UAB. Day, Phillips and Tuscher are, respectively, associate professor, graduate student and postdoctoral fellow in the UAB Department of Neurobiology.

Support came from National Institutes of Health grants MH114990, DA039650 and DA048348; UAB’s Pittman Scholars Program, AMC21 Scholars Program and Civitan International Research Center; and a Brain and Behavior Research Foundation Young Investigator grant.

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Engineers enlist AI to help scale up advanced solar cell manufacturing

Perovskites are a family of materials that are currently the leading contender to potentially replace today’s silicon-based solar photovoltaics. They hold the promise of panels that are far thinner and lighter, that could be made with ultra-high throughput at room temperature instead of at hundreds of degrees, and that are cheaper and easier to transport and install. But bringing these materials from controlled laboratory experiments into a product that can be manufactured competitively has been a long struggle.

Manufacturing perovskite-based solar cells involves optimizing at least a dozen or so variables at once, even within one particular manufacturing approach among many possibilities. But a new system based on a novel approach to machine learning could speed up the development of optimized production methods and help make the next generation of solar power a reality.

The system, developed by researchers at MIT and Stanford University over the last few years, makes it possible to integrate data from prior experiments, and information based on personal observations by experienced workers, into the machine learning process. This makes the outcomes more accurate and has already led to the manufacturing of perovskite cells with an energy conversion efficiency of 18.5 percent, a competitive level for today’s market.

The research is reported in the journal Joule, in a paper by MIT professor of mechanical engineering Tonio Buonassisi, Stanford professor of materials science and engineering Reinhold Dauskardt, recent MIT research assistant Zhe Liu, Stanford doctoral graduate Nicholas Rolston, and three others.

Perovskites are a group of layered crystalline compounds defined by the configuration of the atoms in their crystal lattice. There are thousands of such possible compounds and many different ways of making them. While most lab-scale development of perovskite materials uses a spin-coating technique, that’s not practical for larger-scale manufacturing, so companies and labs around the world have been searching for ways of translating these lab materials into a practical, manufacturable product.

“There’s always a big challenge when you’re trying to take a lab-scale process and then transfer it to something like a startup or a manufacturing line,” says Rolston, who is now an assistant professor at Arizona State University. The team looked at a process that they felt had the greatest potential, a method called rapid spray plasma processing, or RSPP.

The manufacturing process would involve a moving roll-to-roll surface, or series of sheets, on which the precursor solutions for the perovskite compound would be sprayed or ink-jetted as the sheet rolled by. The material would then move on to a curing stage, providing a rapid and continuous output “with throughputs that are higher than for any other photovoltaic technology,” Rolston says.

“The real breakthrough with this platform is that it would allow us to scale in a way that no other material has allowed us to do,” he adds. “Even materials like silicon require a much longer timeframe because of the processing that’s done. Whereas you can think of [this approach as more] like spray painting.”

Within that process, at least a dozen variables may affect the outcome, some of them more controllable than others. These include the composition of the starting materials, the temperature, the humidity, the speed of the processing path, the distance of the nozzle used to spray the material onto a substrate, and the methods of curing the material. Many of these factors can interact with each other, and if the process is in open air, then humidity, for example, may be uncontrolled. Evaluating all possible combinations of these variables through experimentation is impossible, so machine learning was needed to help guide the experimental process.

But while most machine-learning systems use raw data such as measurements of the electrical and other properties of test samples, they don’t typically incorporate human experience such as qualitative observations made by the experimenters of the visual and other properties of the test samples, or information from other experiments reported by other researchers. So, the team found a way to incorporate such outside information into the machine learning model, using a probability factor based on a mathematical technique called Bayesian Optimization.

Using the system, he says, “having a model that comes from experimental data, we can find out trends that we weren’t able to see before.” For example, they initially had trouble adjusting for uncontrolled variations in humidity in their ambient setting. But the model showed them “that we could overcome our humidity challenges by changing the temperature, for instance, and by changing some of the other knobs.”

The system now allows experimenters to much more rapidly guide their process in order to optimize it for a given set of conditions or required outcomes. In their experiments, the team focused on optimizing the power output, but the system could also be used to simultaneously incorporate other criteria, such as cost and durability — something members of the team are continuing to work on, Buonassisi says.

The researchers were encouraged by the Department of Energy, which sponsored the work, to commercialize the technology, and they’re currently focusing on tech transfer to existing perovskite manufacturers. “We are reaching out to companies now,” Buonassisi says, and the code they developed has been made freely available through an open-source server. “It’s now on GitHub, anyone can download it, anyone can run it,” he says. “We’re happy to help companies get started in using our code.”

Already, several companies are gearing up to produce perovskite-based solar panels, even though they are still working out the details of how to produce them, says Liu, who is now at the Northwestern Polytechnical University in Xi’an, China. He says companies there are not yet doing large-scale manufacturing, but instead starting with smaller, high-value applications such as building-integrated solar tiles where appearance is important. Three of these companies “are on track or are being pushed by investors to manufacture 1 meter by 2-meter rectangular modules [comparable to today’s most common solar panels], within two years,” he says.

‘The problem is, they don’t have a consensus on what manufacturing technology to use,” Liu says. The RSPP method, developed at Stanford, “still has a good chance” to be competitive, he says. And the machine learning system the team developed could prove to be important in guiding the optimization of whatever process ends up being used.

“The primary goal was to accelerate the process, so it required less time, less experiments, and less human hours to develop something that is usable right away, for free, for industry,” he says.

The team also included Austin Flick and Thomas Colburn at Stanford and Zekun Ren at the Singapore-MIT Alliance for Science and Technology (SMART). In addition to the Department of Energy, the work was supported by a fellowship from the MIT Energy Initiative, the Graduate Research Fellowship Program from the National Science Foundation, and the SMART program.

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Rain, floods and green infrastructure: Are cities mitigating the hazards equitably?

As cities grow, the area of impervious surfaces they cover grows. In cities across the US, roads, rooftops, parking lots, sidewalks and driveways increased by an average of 326,000 hectares per year between 2012 and 2017.

When it rains, stormwater gathers on these surfaces or flows into gutters, storm drains and sewer systems. However, extreme precipitation events can overwhelm a city’s capacity to transport stormwater, resulting in urban floods. The introduction of green infrastructures (GI), such as bioswales with permeable surfaces, has provided municipalities with a new tool to manage flood risk associated with rainfall. Cities including Portland, Phoenix and Atlanta have developed plans and invested in implementing GI to mitigate the risk of floods.

New research from Portland State University combines demographic data with the distribution of GI and geographic areas prone to rainwater flooding in Portland, Phoenix and Atlanta and asks whether these cities are equitably building GI to mitigate flood risks.

The paper, “Urban flood risk and green infrastructure: Who is exposed to risk and who benefits from investment? A case study of three US cities,” appears in Landscape and Urban Planning.

According to the paper’s lead author, Arun Pallathadka, a Ph.D. student in the Earth, Environment and Society program at Portland State, the research team found that the placement of GI in each of the cities inconsistently overlapped with areas prone to rainwater flooding, and non-white and low-income populations were more vulnerable to flood risk. Portland and Phoenix have increased investments in GI in neighborhoods with higher populations of non-white and low-income residents, marking a transition to more equitable flood risk management. In Atlanta, the risk of rainwater flooding was relatively low for non-white and low-income residents, though there was a substantial disparity in GI coverage.

“Flooding is the costliest natural hazard,” Pallathadka said. “But when we talk about flooding, the focus is often on the floodplain, on rivers. But with climate change, we’re expecting an increase in flooding associated with rainfall events. We wanted to know where the hotspots in cities are associated with a risk of flooding from rain, who are the people living in those communities, and where are cities placing infrastructure to help reduce the hazards.”

In addition to the spatial, temporal and demographic analysis, the research team, which includes Heejun Chang, a professor of geography at Portland State and Jason Sauer and Nancy Grimm of Arizona State University, developed that can be used by researchers, city planners and policymakers to categorize neighborhood risk levels. Cities can use the tool to help guide investments in GI to neighborhoods most at risk of flooding from rainfall events. A conceptual framework for understanding the distribution and implications of urban pluvial flood risk and green infrastructure (GI) in urban communities.

The methods deployed by the team provide cities with a novel approach to assessing the need for GI in neighborhoods prone to flooding associated with rainwater while also planning for the equitable distribution of those resources as they move ahead under the threat of increasing extreme precipitation events associated with a warming planet.

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Materials provided by Portland State University. Original written by Shaun McGillis. Note: Content may be edited for style and length.

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US Nationwide maps of bird species can help protect biodiversity

Researchers at the University of Wisconsin-Madison developed the maps at a fine-enough resolution to help conservation managers focus their efforts where they are most likely to help birds — in individual counties or forests, rather than across whole states or regions.

The maps span the contiguous U.S. and predict the diversity of birds that live in a given area, related by traits such as nesting on the ground or being endangered. Those predictions are based on both detailed observations of birds and environmental factors that affect bird ranges, such as the degree of forest cover or temperature in an area.

“With these maps, managers have a tool they didn’t have before that allows them to get both a broad perspective as well as information at the level of detail that’s necessary for their action plans,” says Anna Pidgeon, a professor of forest and wildlife ecology at UW-Madison who helped lead the development of the maps.

Pidgeon worked with UW-Madison professor Volker Radeloff, postdoctoral researcher and lead author Kathleen Carroll and others to publish the research and the final maps April 11 in the journal Ecological Applications. The maps are available for public download from the open-access website Dryad.

The research was designed to address two outstanding problems in conservation.

“Across the world we’re seeing huge species losses. In North America, 3 billion birds have been lost since 1970. This is across virtually all habitat types,” says Carroll. “And we’re seeing a disconnect between what scientists produce for conservation and how that translates to boots-on-the-ground management.”

Many resources previously available to conservation managers, such as species range maps, are both at too broad of a scale to be useful and not rigorously tested for accuracy.

To overcome those challenges, Carroll and her team wanted to develop data-driven maps of existing bird biodiversity. They produced the maps by extrapolating observations of birds from scientific surveys to mile-by-mile predictions of where different species really live. Those predictions were based on factors including rainfall, the degree of forest cover and the extent of human influence on the environment, such as the presence of cities or farms.

To improve the predictive power of their maps, the scientists clustered individual species by behavior, habitat, diet, or conservation status — such as fruit eaters or forest dwellers. These groups are called guilds. Many conservation decisions happen at the guild level, rather than at the level of species. Guilds can also make up for limited information on the most endangered species.

The final maps cover 19 different guilds at resolutions of 0.5, 2.5 and 5 kilometers. While the finest-grained maps were not as accurate, the 2.5-kilometer-resolution maps provided a good balance of accuracy and usefulness for realistic conservation needs, say the scientists. At the 5-kilometer resolution, the maps provide the greatest accuracy and are useful to conservationists operating across large areas.

“We see this being really applicable for things like forest management action plans for the U.S. Forest Service,” says Carroll. “They can pull up these maps for a group of interest, and they can get a very clear indication of what areas where they might want to limit human use.”

The maps may also help private land conservancies decide where to prioritize limited resources to maximize biodiversity protections.

Carroll is now working to extend the analysis down to individual species, rather than guilds made up of multiple species. The increased level of detail could help specialist conservation managers improve their work, especially those aiming to protect a single species.

This work was supported in part by the U.S. Geological Survey Landsat Science Team (grants G17PS00256) and the NASA Biodiversity and Ecological Forecasting Program (grant 20-BIODIV20-00460.

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Materials provided by University of Wisconsin-Madison. Original written by Eric Hamilton. Note: Content may be edited for style and length.

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A new toolkit to engineer safe and efficient therapeutic cells

Therapies based on engineered immune cells have recently emerged as a promising approach in the treatment of cancer. Compared to traditional drugs, engineered immune cells are more precise and sophisticated in their ability to detect and eliminate cancer cells.

But despite their promise, cell-based therapies still face important limitations, including toxicity and the possibility that they could attack healthy cells. In addition, scientists don’t have a good handle on how to modify existing therapeutic cells to expand their applications or better control their activity.

To overcome these limitations, researchers at Gladstone Institutes and UC San Francisco (UCSF) undertook a systematic analysis of the molecular building blocks used to engineer therapeutic cells. Their work, reported in the journal Cell, resulted in a comprehensive rule book for the design of therapeutic cells with improved specificity and safety, and for the eventual customization of cell-based therapies.

“We have identified principles that should greatly facilitate the engineering of therapeutic cells with greater sensitivity, accuracy, and safety than was possible before,” says Kole Roybal, PhD, an associate professor in the Department of Microbiology and Immunology at UCSF, an affiliate investigator at Gladstone Institutes and core member of the Gladstone-UCSF Institute of Genomic Immunology, a Parker Institute for Cancer Immunotherapy investigator, and the study’s senior author. “Our work will provide biomedical researchers with a toolkit for directing a range of cell-based therapies to their intended targets and for programming their therapeutic activities.”

Building a Better Receptor

At the core of most therapeutic cells is a molecule called a receptor. Receptors are large proteins that straddle the cell’s outer membrane. Their outer portion recognizes a specific target (for instance a protein on the surface of a cancer cell) and their inner portion tells the cell what to do upon recognizing this target. One way to engineer a therapeutic cell is to insert in a cell — often an immune cell called a T cell — a synthetic receptor made by piecing together fragments of known receptors.

This approach was used to create CAR-T cells, which have proven very effective at eliminating some types of blood cancers. CAR-T cells harbor a “chimeric antigen receptor” (CAR) that is based on a receptor normally found in T cells.

Starting with a different backbone, Roybal previously developed a receptor called synNotch that can direct T cells to better recognize and kill solid tumors. Since this early stage research, Roybal’s lab has shown how synNotch can be used in combination with CARs to develop next-generation cell therapies for ovarian cancer and mesothelioma. The synNotch receptor allows scientists to precisely control when and where the therapeutic T cell is active.

“These smart cell therapies can unleash potent therapeutic activity precisely at the site of disease, improving the efficacy of the therapy and reducing the chance of life-threatening toxicities seen in patients,” says Roybal.

However, the original synNotch receptor is difficult to deploy for cell-based therapy in humans. For one thing it is bulky, which makes it difficult to insert into human cells. For another, some of its parts come from mouse, yeast, and viruses instead of human receptors, which could lead to immune rejection of the engineered cells once introduced in a patient.

To understand what they could keep and remove from the synNotch receptor without losing its desirable features, the Roybal team systematically swapped out various portions of the receptor. After inserting the modified receptors in human T cells, the scientists tested their ability to recognize their intended targets and activate the expected response.

“A challenging but fun feat was figuring out how different parts of known receptors function, so that we could take those pieces apart and put them back together in novel ways to meet our design specifications,” says Raymond Liu, PhD, a first author of the study and postdoctoral fellow in Roybal’s lab.

In the end, the team produced a catalog of receptors they dubbed SNIPRs, which are small enough for cost-effective engineering into human cells. They are also made exclusively from human receptor fragments and can detect and respond to even small amounts of their targets. In addition, the activity of SNIPRs can be adapted so that cells that harbor them don’t just kill target cells, but can also deliver specific molecules to precise disease locations.

“Understanding the rules of receptor design allowed us to build receptors that are more effective and also better suited for clinical translation,” says Iowis Zhu, a graduate student in the Roybal Lab and the other first author of the new study.

A Platform for Next-Generation Cell Therapy

The researchers next assessed the ability of these optimized receptors to clear tumors in mouse models of leukemia, mesothelioma, and ovarian cancer.

To reduce the chances of killing non-target cells, they combined a SNIPR designed to recognize one molecule on the tumor with a CAR receptor tuned to another tumor molecule. Moreover, they made the production of the CAR receptor dependent on the activation of the SNIPR receptor. This way, only cells carrying the targets of both the synNotch and the CAR receptors would be killed, while cells carrying only one target would not.

In each of the three cancer types they tested, this two-step targeting strategy led to more selective elimination of cancer cells than could be achieved with either receptor alone, highlighting the promise of this approach to reduce off-target toxicity of cell therapies.

Cell therapies based on SNIPRs are now being optimized for the treatment of ovarian cancer, renal cancer, prostate cancer, and glioblastoma in both the academic setting and a company called Arsenal Bio, co-founded by Roybal.

And cancer may not be the only condition that could be treated with SNIPR-based cell therapy.

This receptor system is also amenable to enhancing the anti-inflammatory activity of immune cells for the treatment of autoimmunity. In addition, SNIPRs could be used to target stem cells or other cell types to detect tissue damage and induce tissue repair or the reversal of fibrosis.

“Engineered cells have the potential to operate as much smarter therapeutics than traditional small molecules and biologics,” says Roybal. “We’re hoping our new receptor system will serve as a technology platform enabling scientists and clinicians to design safer, targeted, and more effective cell-based therapies against cancer and many other diseases.”

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MND: ‘It’s like a hand grenade going off in your body’

A man living with motor neurone disease says he tries to stay upbeat despite the “cruel” illness.

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Brain cancer DNA research hopes to speed up diagnosis

More than 200 brain tumour patients are taking part in research hoping to yield new personalised treatments.

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Drug reduced frequency of breathing pauses in sleep apnea

A new University of Gothenburg study has paved the way for the first drug treatment for sleep apnea. Compared to before receiving the treatment, breathing pauses decreased with on average more than 20 per hour for patients given the drug.

The treatment that has been tested is carbonic anhydrase (CA) inhibition, CA being an enzyme that serves to maintain a balance between carbonic acid and carbon dioxide in the body. Several drugs with CA inhibitory properties are already available on the market, and used for treatment of glaucoma, epilepsy and other disorders.

Previous research has not systematically tested whether CA inhibitors also might be used to treat obstructive sleep apnea. The current study was a randomized double-blind clinical trial, and 59 patients with moderate or severe sleep apnea completed it. Patients were randomly assigned to two groups receiving either 400 or 200 mg of the CA inhibitor, and a third group (the control group) that received placebo. The study lasted for four weeks.

Fewer breathing pauses

The results show that, overall, the treatment reduced the number of breathing pauses and promoted oxygenation during the night. A few patients experienced side effects, such as headache and breathlessness, which were more common in those receiving the highest dose.

The study results together with established safety data of the drug sulthiame provide support for continued research on CA inhibition as a new potential treatment for obstructive sleep apnea.

“Among the patients who received the higher dosage of the drug, the number of breathing pauses decreased by approximately 20 per hour. For just over a third of patients in the study, only half of their breathing pauses were left, and in one in five the number fell by at least 60 percent,” says Jan Hedner, Professor of Pulmonary Medicine.

The fact that several approved drugs in the CA inhibitor category are available on the market makes fast-tracking development of an approved drug for sleep apnea practicable. The drug used in this clinical trial was sulthiame, which is sometimes used to treat epilepsy in children.

Treatment options needed

Today, treatment for a patient with sleep apnea is either an oral appliance therapy or a CPAP (Continuous Positive Airway Pressure) mask. Both help to maintain airway patency during sleep.

“These therapy options take time to get used to and, since they frequently are perceived as intrusive or bulky. Insufficient user time is therefore common. If we develop an effective drug, it will therefore make life easier for many patients and, in the long run, potentially also save more lives,” says Ludger Grote, Senior Lecturer at Sahlgrenska Academy, University of Gothenburg.

The German pharmaceutical company Desitin Arzneimittel GmbH funded the trial, and the results are published in the American Journal of Respiratory and Critical Care Medicine.

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

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Light amplification accelerates chemical reactions in aerosols

Aerosols in the atmosphere react to incident sunlight. This light is amplified in the interior of the aerosol droplets and particles, accelerating reactions. ETH researchers have now been able to demonstrate and quantify this effect and recommend factoring it into future climate models.

Liquid droplets and very fine particles can trap light — similar to how light can be caught between two mirrors. As a result, the intensity of the light inside them is amplified. This also happens in very fine water droplets and solid particles in our atmosphere, i.e. aerosols. Using modern X-ray microscopy, chemists at ETH Zurich and the Paul Scherrer Institute (PSI) have now investigated how light amplification affects photochemical processes that take place in the aerosols. They were able to demonstrate that light amplification causes these chemical processes to be two to three times faster on average than they would be without this effect.

Using the Swiss Light Source at the PSI, the researchers studied aerosols consisting of tiny particles of iron(III) citrate. Exposure to light reduces this compound to iron(II) citrate. X-ray microscopy makes it possible to distinguish areas within the aerosol particles composed of iron(III) citrate from those made up of iron(II) citrate down to a precision of 25 nanometres. In this way, the scientists were able to observe and map in high resolution the temporal sequence of this photochemical reaction in individual aerosol particles.

Decay upon exposure to light

“For us, iron(III) citrate was a representative compound that was easy to study with our method,” says Pablo Corral Arroyo, a postdoc in the group headed by ETH Professor Ruth Signorell and a lead author of the study. Iron(III) citrate stands in for a whole range of other chemical compounds that can occur in the aerosols of the atmosphere. Many organic and inorganic compounds are light-sensitive, and when exposed to light, they can break down into smaller molecules, which can be gaseous and therefore escape. “The aerosol particles lose mass in this way, changing their properties,” Signorell explains. Among other things, they scatter sunlight differently, which affects weather and climate phenomena. In addition, their characteristics as condensation nuclei in cloud formation change.

As such, the results also have an effect on climate research. “Current computer models of global atmospheric chemistry don’t yet take this light amplification effect into account,” ETH Professor Signorell says. The researchers suggest incorporating the effect into these models in future.

Non-uniform reaction times in the particles

Now precisely mapped and quantified, the light amplification in the particles comes about through resonance effects. The light intensity is greatest on the side of the particle opposite the one the light is shining on. “In this hotspot, photochemical reactions are up to ten times faster than they would be without the resonance effect,” says Corral Arroyo. Averaged over the entire particle, this gives an acceleration by the above-mentioned factor of two to three. Photochemical reactions in the atmosphere usually last several hours or even days.

Using the data from their experiment, the researchers were able to create a computer model to estimate the effect on a range of other photochemical reactions of typical aerosols in the atmosphere. It turned out that the effect does not pertain just to iron(III) citrate particles, but all aerosols — particles or droplets — made of compounds that can react with light. And these reactions are also two to three times faster on average.

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Materials provided by ETH Zurich. Original written by Fabio Bergamin. Note: Content may be edited for style and length.

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New research sheds fresh light on the ‘presenteeism’

Employees who are unwell only engage in presenteeism when they have not met their daily work goals, according to new research from Trinity College Dublin.

The study, published in the Journal of Occupational Health Psychology recently, also found that working on a day when you feel ill drains mental energy which cannot be recovered the next day.

The study seeks to shed further light on the phenomenon of ‘presenteeism’ — defined by the researchers as continuing to work when experiencing ill-health. The practice has been labelled an ‘800-pound gorilla’ by researchers in occupational health psychology because of the tremendous costs it inflicts on employees and organisations alike. These costs include burnout, impaired workability, and productivity loss.

This study led by Dr Wladislaw Rivkin, Associate Professor in Organisational Behaviour, Trinity, deepens our understanding of the harmful impact of presenteeism on employee effectiveness by demonstrating that depletion of mental resources is a key mechanism responsible for these harmful effects.

The research involved 126 employees logging their daily productivity across 12 workdays, resulting in 995 daily work observations. It was conducted during the COVID-19 lockdown in 2020 when all participants were working from home.

Dr Rivkin commented:

“It is crucial to tackle daily presenteeism, especially for remote workers. Managers should openly discourage presenteeism by reassuring team members that if they feel unwell it is acceptable to reduce their daily work goals and instead tend to their health. In light of the energy-depleting nature of presenteeism if employees engage in presenteeism they should work on tasks that are inherently pleasant rather than tedious tasks that further drain their energy.

“So, while it may seem a good idea to work despite ill health to deliver on work goals our research shows that this has a knock-on effect for remote workers’ performance on the next day as presenteeism drains employees’ psychological energy, which cannot be fully recovered after work.”

The full paper was entitled “Should I stay or should I go? The role of daily presenteeism as an adaptive response to perform at work despite somatic complaints for employee effectiveness.”

Wlad Rivkin is an Associate Professor in Organisational Behaviour and Work Psychology whose research focuses on burnout, stress and other demands that people experience at work as well as what organisations can do to protect employee wellbeing and maintain their effectiveness. Other recent research projects include studies on the impact of commuting on employee wellbeing, the role of willpower in overcoming the negative effects of a bad night’s sleep and how smartphone use during non-work time impacts on sleep quality.

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Materials provided by Trinity College Dublin. Note: Content may be edited for style and length.

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