At the latest, the Russia-Ukraine conflict revealed loud and clear that the global food supply chain acts as a complex network, connecting nations and facilitating the spread of disruptions from local to distant regions. “However, previous studies often focus on direct dependencies and overlook indirect dependencies resulting from the unavailability of essential inputs, making a comprehensive assessment of the global food system difficult,” emphasizes research director Stefan Thurner of the Complexity Science Hub.

INDIRECT EFFECTS OFTEN EXCEED DIRECT EFFECTS

To bridge this gap, the research team developed a dynamic global food system model, incorporating data from 192 countries and territories and encompassing 125 food and agricultural products. “This model enabled us to simulate shocks to specific products and countries, closely monitoring the subsequent effects across the entire supply chain,” explains Moritz Laber of the Complexity Science Hub. By quantifying the relative reduction in product availability compared to a baseline scenario (without the shock), the researchers gained valuable insights into the magnitude of these shocks. Remarkably, they found that indirect effects often exceeded direct effects. For example, a shock to Ukrainian corn production led to a 13% decline in pork availability in Southern Europe. In comparison, a shock to Ukrainian pork production had a negligible effect of less than 1%.

UP TO 85% LOSS OF MAIZE

In a worst-case scenario simulation, where agricultural production in Ukraine was completely lost due to the Russia-Ukraine conflict, the study unveiled diverse effects on products and regions worldwide. “The loss of grains, particularly maize, reached up to 85%, while edible oils, especially sunflower oil, experienced losses of up to 89%. Additionally, certain meat types, such as poultry, suffered losses of up to 25% in various countries,” says Laber. The number of products for which a region is dependent on Ukraine varies greatly: Southern Europe is the most affected, with 19 out of 125 products with losses of more than 10%, followed by West Asia and North Africa, where this is the case for 15 and 11 products respectively.

These findings emphasize that localized production disruptions have far-reaching implications, extending beyond geographic boundaries through trade relationships and the entire production chain. Consequently, it is imperative to consider both direct and indirect effects when estimating losses and formulating effective interventions.

RISK NOT ONLY FROM WARS

As the Russia-Ukraine conflict enters its second year, food prices are still above 2021 levels, according to the European Council. In addition, various events, including extreme weather events, economic crises, and geopolitical tensions, can trigger similar disruptions. This underscores the importance of exploring interdependencies within global food supply chains and gaining a comprehensive understanding of the direct and indirect impacts of local shocks to raise awareness among policymakers and stakeholders of otherwise overlooked risks within the global food system.

These research findings are a valuable first leap in understanding the complex dynamics of global food supply chains and their vulnerability to local shocks. Further research is needed to map them at a more granular level considering individual products and subnational scales at a higher temporal resolution. Moreover, at present, the model assumes that countries do not change their trading partners after a shock. However, restructuring trade relations may exacerbate existing inequalities, as wealthier countries may secure remaining resources at higher prices from alternative suppliers.

In March, the CSH co-founded the Austrian Supply Chain Intelligence Institute (ASCII) to contribute even more to making supply dependencies visible in the future.

Some implants are hard and bulky, while others are flexible and thin. But no matter their form and function, nearly all implants incorporate electrodes — small conductive elements that attach directly to target tissues to electrically stimulate muscles and nerves.

Implantable electrodes are predominantly made from rigid metals that are electrically conductive by nature. But over time, metals can aggravate tissues, causing scarring and inflammation that in turn can degrade an implant’s performance.

Now, MIT engineers have developed a metal-free, jelly-like material that is as soft and tough as biological tissue and can conduct electricity similarly to conventional metals. The material can be made into a printable ink, which the researchers patterned into flexible, rubbery electrodes. The new material, which is a type of high-performance conducting polymer hydrogel, may one day replace metals as functional, gel-based electrodes, with the look and feel of biological tissue.

“This material operates the same as metal electrodes but is made from gels that are similar to our bodies, and with similar water content,” says Hyunwoo Yuk SM ’16 PhD ’21, co-founder of SanaHeal, a medical device startup. “It’s like an artificial tissue or nerve.”

“We believe that for the first time, we have a tough, robust, Jell-O-like electrode that can potentially replace metal to stimulate nerves and interface with the heart, brain, and other organs in the body,” adds Xuanhe Zhao, professor of mechanical engineering and of civil and environmental engineering at MIT.

Zhao, Yuk, and others at MIT and elsewhere report their results in Nature Materials. The study’s co-authors include first author and former MIT postdoc Tao Zhou, who is now an assistant professor at Penn State University, and colleagues at Jiangxi Science and Technology Normal University and Shanghai Jiao Tong University.

A true challenge

The vast majority of polymers are insulating by nature, meaning that electricity does not pass easily through them. But there exists a small and special class of polymers that can in fact pass electrons through their bulk. Some conductive polymers were first shown to exhibit high electrical conductivity in the 1970s — work that was later awarded a Nobel Prize in Chemistry.

Recently, researchers including those in Zhao’s lab have tried using conductive polymers to fabricate soft, metal-free electrodes for use in bioelectronic implants and other medical devices. These efforts have aimed to make soft yet tough, electrically conductive films and patches, primarily by mixing particles of conductive polymers, with hydrogel — a type of soft and spongy water-rich polymer.

Researchers hoped the combination of conductive polymer and hydrogel would yield a flexible, biocompatible, and electrically conductive gel. But the materials made to date were either too weak and brittle, or they exhibited poor electrical performance.

“In gel materials, the electrical and mechanical properties always fight each other,” Yuk says. “If you improve a gel’s electrical properties, you have to sacrifice mechanical properties, and vice versa. But in reality, we need both: A material should be conductive, and also stretchy and robust. That was the true challenge and the reason why people could not make conductive polymers into reliable devices entirely made out of gel.”

Electric spaghetti

In their new study, Yuk and his colleagues found they needed a new recipe to mix conductive polymers with hydrogels in a way that enhanced both the electrical and mechanical properties of the respective ingredients.

“People previously relied on homogenous, random mixing of the two materials,” Yuk says.

Such mixtures produced gels made of randomly dispersed polymer particles. The group realized that to preserve the electrical and mechanical strengths of the conductive polymer and the hydrogel respectively, both ingredients should be mixed in a way that they slightly repel — a state known as phase separation. In this slightly separated state, each ingredient could then link its respective polymers to form long, microscopic strands, while also mixing as a whole.

“Imagine we are making electrical and mechanical spaghetti,” Zhao offers. “The electrical spaghetti is the conductive polymer, which can now transmit electricity across the material because it is continuous. And the mechanical spaghetti is the hydrogel, which can transmit mechanical forces and be tough and stretchy because it is also continuous.”

The researchers then tweaked the recipe to cook the spaghettified gel into an ink, which they fed through a 3D printer, and printed onto films of pure hydrogel, in patterns similar to conventional metal electrodes.

“Because this gel is 3D-printable, we can customize geometries and shapes, which makes it easy to fabricate electrical interfaces for all kinds of organs,” says first-author Zhou.

The researchers then implanted the printed, Jell-O-like electrodes onto the heart, sciatic nerve, and spinal cord of rats. The team tested the electrodes’ electrical and mechanical performance in the animals for up to two months and found the devices remained stable throughout, with little inflammation or scarring to the surrounding tissues. The electrodes also were able to relay electrical pulses from the heart to an external monitor, as well as deliver small pulses to the sciatic nerve and spinal cord, which in turn stimulated motor activity in the associated muscles and limbs.

Going forward, Yuk envisions that an immediate application for the new material may be for people recovering from heart surgery.

“These patients need a few weeks of electrical support to avoid heart attack as a side effect of surgery,” Yuk says. “So, doctors stitch a metallic electrode on the surface of the heart and stimulate it over weeks. We may replace those metal electrodes with our gel to minimize complications and side effects that people currently just accept.”

The team is working to extend the material’s lifetime and performance. Then, the gel could be used as a soft electrical interface between organs and longer-term implants, including pacemakers and deep-brain stimulators.

“The goal of our group is to replace glass, ceramic, and metal inside the body, with something like Jell-O so it’s more benign but better performance, and can last a long time,” Zhao says. “That’s our hope.”

This research is supported, in part, by the National Institutes of Health.

Based on climate models, scientists previously estimated humans pumped 2,150 gigatons of groundwater, equivalent to more than 6 millimeters (0.24 inches) of sea level rise, from 1993 to 2010. But validating that estimate is difficult.

One approach lies with the Earth’s rotational pole, which is the point around which the planet rotates. It moves during a process called polar motion, which is when the position of the Earth’s rotational pole varies relative to the crust. The distribution of water on the planet affects how mass is distributed. Like adding a tiny bit of weight to a spinning top, the Earth spins a little differently as water is moved around.

“Earth’s rotational pole actually changes a lot,” said Ki-Weon Seo, a geophysicist at Seoul National University who led the study. “Our study shows that among climate-related causes, the redistribution of groundwater actually has the largest impact on the drift of the rotational pole.”

Water’s ability to change the Earth’s rotation was discovered in 2016, and until now, the specific contribution of groundwater to these rotational changes was unexplored. In the new study, researchers modeled the observed changes in the drift of Earth’s rotational pole and the movement of water — first, with only ice sheets and glaciers considered, and then adding in different scenarios of groundwater redistribution.

The model only matched the observed polar drift once the researchers included 2150 gigatons of groundwater redistribution. Without it, the model was off by 78.5 centimeters (31 inches), or 4.3 centimeters (1.7 inches) of drift per year.

“I’m very glad to find the unexplained cause of the rotation pole drift,” Seo said. “On the other hand, as a resident of Earth and a father, I’m concerned and surprised to see that pumping groundwater is another source of sea-level rise.”

“This is a nice contribution and an important documentation for sure,” said Surendra Adhikari, a research scientist at the Jet Propulsion Laboratory who was not involved in this study. Adhikari published the 2016 paper on water redistribution impacting rotational drift. “They’ve quantified the role of groundwater pumping on polar motion, and it’s pretty significant.”

The location of the groundwater matters for how much it could change polar drift; redistributing water from the midlatitudes has a larger impact on the rotational pole. During the study period, the most water was redistributed in western North America and northwestern India, both at midlatitudes.

Countries’ attempts to slow groundwater depletion rates, especially in those sensitive regions, could theoretically alter the change in drift, but only if such conservation approaches are sustained for decades, Seo said.

The rotational pole normally changes by several meters within about a year, so changes due to groundwater pumping don’t run the risk of shifting seasons. But on geologic time scales, polar drift can have an impact on climate, Adhikari said.

The next step for this research could be looking to the past.

“Observing changes in Earth’s rotational pole is useful for understanding continent-scale water storage variations,” Seo said. “Polar motion data are available from as early as the late 19^th century. So, we can potentially use those data to understand continental water storage variations during the last 100 years. Were there any hydrological regime changes resulting from the warming climate? Polar motion could hold the answer.”

As the material absorbs water vapor, it can swell to make room for more moisture. Even in very dry conditions, with 30 percent relative humidity, the material can pull vapor from the air and hold in the moisture without leaking. The water could then be heated and condensed, then collected as ultrapure water.

The transparent, rubbery material is made from hydrogel, a naturally absorbent material that is also used in disposable diapers. The team enhanced the hydrogel’s absorbency by infusing it with lithium chloride — a type of salt that is known to be a powerful dessicant.

The researchers found they could infuse the hydrogel with more salt than was possible in previous studies. As a result, they observed that the salt-loaded gel absorbed and retained an unprecedented amount of moisture, across a range of humidity levels, including very dry conditions that have limited other material designs.

If it can be made quickly, and at large scale, the superabsorbent gel could be used as a passive water harvester, particularly in the desert and drought-prone regions, where the material could continuously absorb vapor, that could then be condensed into drinking water. The researchers also envision that the material could be fit onto air conditioning units as an energy-saving, dehumidifying element.

“We’ve been application-agnostic, in the sense that we mostly focus on the fundamental properties of the material,” says Carlos Díaz-Marin, a mechanical engineering graduate student and member of the Device Research Lab at MIT. “But now we are exploring widely different problems like how to make air conditioning more efficient and how you can harvest water. This material, because of its low cost and high performance, has so much potential.”

Díaz-Marin and his colleagues have published their results in a paper appearing today in Advanced Materials. The study’s MIT co-authors are Gustav Graeber, Leon Gaugler, Yang Zhong, Bachir El Fil, Xinyue Liu, and Evelyn Wang.

“Best of both worlds”

In MIT’s Device Research Lab, researchers are designing novel materials to solve the world’s energy and water challenges. In looking for materials that can help to harvest water from the air, the team zeroed in on hydrogels — slippery, stretchy gels that are mostly made from water and a bit of cross-linked polymer. Hydrogels have been used for years as absorbent material in diapers because they can swell and soak up a large amount of water when it comes in contact with the material.

“Our question was, how can we make this work just as well to absorb vapor from the air?” Díaz-Marin says.

He and his colleagues dug through the literature and found that others had experimented with mixing hydrogels with various salts. Certain salts, such as the rock salt used to melt ice, are very efficient at absorbing moisture, including water vapor. And the best among them is lithium chloride, a salt that is capable of absorbing over 10 times its own mass in moisture. Left in a pile on its own, lithium chloride could attract vapor from the air, though the moisture would only pool around the salt, with no means of retaining the absorbed water.

So, researchers have attempted to infuse the salt into hydrogel — producing a material that could both hold in moisture and swell to accommodate more water.

“It’s the best of both worlds,” says Graeber, who is now a principal investigator at Humboldt University in Berlin. “The hydrogel can store a lot of water, and the salt can capture a lot of vapor. So it’s intuitive that you’d want to combine the two.”

Time to load

But the MIT team found that others reached a limit to the amount of salt they could load into their gels. The best performing samples to date were hydrogels that were infused with 4 to 6 grams of salt per gram of polymer. These samples absorbed about 1.5 grams of vapor per gram of material in dry conditions of 30 percent relative humidity.

In most studies, researchers had previously synthesized samples by soaking hydrogels in salty water and waiting for the salt to infuse into the gels. Most experiments ended after 24 to 48 hours, as researchers found the process was too slow, and not very much salt ended up in the gels. When they tested the resulting material’s ability to absorb water vapor, the samples soaked up very little, as they contained little salt to absorb the moisture in the first place.

What would happen if the material synthesis was allowed to go on, say, for days, and even weeks? Could a hydrogel absorb even more salt, if given enough time? For an answer, the MIT team carried out experiments with polyacrylamide (a common hydrogel) and lithium chloride (a superabsorbent salt). After synthesizing tubes of hydrogel through standard mixing methods, the researchers sliced the tubes into thin disks and dropped each disk into a solution of lithium chloride with a different salt concentration. They took the disks out of solution each day to weigh them and determine the amount of salt that had infused into the gels, then returned them to their solutions.

In the end, they found that, indeed, given more time, hydrogels took up more salt. After soaking in salty solution for 30 days, hydrogels incorporated up to 24, versus the previous record of 6 grams of salt per gram of polymer.

The team then put various samples of the salt-laden gels through absorption tests across a range of humidity conditions. They found that the samples could swell and absorb more moisture at all humidity levels, without leaking. Most notably, the team reports that at very dry conditions of 30 percent relative humidity, the gels captured a “record-breaking” 1.79 grams of water per gram of material.

“Any desert during the night would have that low relative humidity, so conceivably, this material could generate water in the desert,” says Díaz-Marin, who is now looking for ways to speed up the material’s superabsorbent properties.

“The big, unexpected surprise was that, with such a simple approach, we were able to get the highest vapor uptake reported to date,” Graeber says. “Now, the main focus will be kinetics and how quickly we can get the material to uptake water. That will allow you to cycle this material very quickly, so that instead of recovering water once a day, you could harvest water maybe 24 times a day.”

This research was supported, in part, by the U.S. Office of Energy Efficiency and Renewable Energy and the Swiss National Science Foundation.

Small-scale field trials in China showed that the newly created rice variety, developed through genome editing of a newly discovered gene, exhibited both high yields and resistance to the fungus that causes a serious disease called rice blast. Rice is an essential crop that feeds half of the world’s population.

Guotian Li, a co-lead author of the study, initially discovered a mutant known as a lesion mimic mutant while working as a postdoctoral scholar in Pamela Ronald’s lab at UC Davis. Ronald is co-lead author and Distinguished Professor in the Department of Plant Pathology and the Genome Center.

“It’s quite a step forward that his team was able to improve this gene, making it potentially useful for farmers. That makes it important,” Ronald said.

The roots of the discovery began in Ronald’s lab, where they created and sequenced 3,200 distinct rice strains, each possessing diverse mutations. Among these strains, Guotian identified one with dark patches on its leaves.

“He found that the strain was also resistant to bacterial infection, but it was extremely small and low yielding,” Ronald said. “These types of ‘lesion mimic’ mutants have been found before but only in a few cases have they been useful to farmers because of the low yield.”

Working with CRISPR

Guotian continued the research when he joined Huazhong Agricultural University in Wuhan, China.

He used CRISPR-Cas9 to isolate the gene related to the mutation and used genome editing to recreate that resistance trait, eventually identifying a line that had good yield and was resistant to three different pathogens, including the fungus that causes rice blast.

In small-scale field trials planted in disease-heavy plots, the new rice plants produced five times more yield than the control rice, which was damaged by the fungus, Ronald said.

“Blast is the most serious disease of plants in the world because it affects virtually all growing regions of rice and also because rice is a huge crop,” Ronald said.

Future applications

The researchers hope to recreate this mutation in commonly grown rice varieties. Currently they have only optimized this gene in a model variety called “Kitaake” that is not grown widely. They also hope to target the same gene in wheat to create disease-resistant wheat.

“A lot of these lesion mimic mutants have been discovered and sort of put aside because they have low yield. We’re hoping that people can go look at some of these and see if they can edit them to get a nice balance between resistance and high yield,” Ronald said.

Rashmi Jain with the UC Davis Department of Plant Pathology and Genome Center also contributed to the research, as did scientists from BGI-Shenzhen, Huazhong Agricultural University, Jiangxi Academy of Agricultural Sciences, Northwest A&F University and Shandong Academy of Agricultural Sciences, China; the Lawrence Berkeley National Laboratory and UC Berkeley; the University of Adelaide, Australia; and the University of Bordeaux, France.

Research in the Ronald lab was supported by the National Science Foundation, the National Institutes of Health and the Joint Bioenergy Institute funded by the US Department of Energy.

Researchers examined illusions in which an object’s surroundings affect the way we see its colour or pattern.

Scientists and philosophers have long debated whether these illusions are caused by neural processing in the eye and low-level visual centres in the brain, or involve higher-level mental processes such as context and prior knowledge.

In the new study Dr Jolyon Troscianko, from the University of Exeter, co-developed a model that suggests simple limits to neural responses — not deeper psychological processes — explain these illusions.

“Our eyes send messages to the brain by making neurones fire faster or slower,” said Dr Troscianko, from the Centre for Ecology and Conservation on Exeter’s Penryn Campus in Cornwall.

“However, there’s a limit to how quickly they can fire, and previous research hasn’t considered how the limit might affect the ways we see colour.”

The model combines this “limited bandwidth” with information on how humans perceive patterns at different scales, together with an assumption that our vision performs best when we are looking at natural scenes.

The model was developed by researchers from the Universities of Exeter and Sussex to predict how animals see colour, but it was also found to correctly predict many visual illusions seen by humans.

“This throws into the air a lot of long-held assumptions about how visual illusions work,” Dr Troscianko said.

He said the findings also shed light on the popularity of high-definition televisions.

“Modern high dynamic range televisions create bright white regions that are over 10,000 times brighter than their darkest black, approaching the contrast levels of natural scenes,” Dr Troscianko added.

“How our eyes and brains can handle this contrast is a puzzle because tests show that the highest contrasts we humans can see at a single spatial scale is around 200:1.

“Even more confusingly, the neurones connecting our eyes to our brains can only handle contrasts of about 10:1.

“Our model shows how neurones with such limited contrast bandwidth can combine their signals to allow us to see these enormous contrasts, but the information is ‘compressed’ — resulting in visual illusions.

“The model shows how our neurones are precisely evolved to use of every bit of capacity.

“For example, some neurones are sensitive to very tiny differences in grey levels at medium-sized scales, but are easily overwhelmed by high contrasts.

“Meanwhile, neurones coding for contrasts at larger or smaller scales are much less sensitive, but can work over a much wider range of contrasts, giving deep black-and-white differences.

“Ultimately this shows how a system with a severely limited neural bandwidth and sensitivity can perceive contrasts larger than 10,000:1.”

The paper, published in the journal PLOS Computational Biology, is entitled: “A model of colour appearance based on efficient coding of natural images.”

Violence during climatic change has evidence in history. University of California, Davis, researchers said they have have found a pattern of increased violence during climatic change in the south central Andes between A.D. 470 and 1500. During that time, which includes the Medieval Climatic Anomaly (ca. A.D. 900-1250), temperatures rose, drought occurred, and the first states of the Andes collapsed.

Climate change and potential competition for limited resources in the south central Andes likely led to violence among people living in the highlands at that time, researchers suggest in a new paper. Their study looked at head injuries of the populations living there at that time, a commonly used proxy among archaeologists for interpersonal violence.

“We found that decreased precipitation predicts increased rates of cranial trauma,” said Thomas J. Snyder, a doctoral candidate in the Department of Anthropology’s Evolutionary Wing and the primary author of the study.

“This observation suggests that climate change in the form of decreased precipitation exerted a significant effect on rates of interpersonal violence in the region.”

The study was published June 5 in Quaternary Research, Cambridge University Press. Co-author of the paper is Randall Haas, formerly of the same lab at UC Davis and currently a professor at Wayne State University.

Violence not found in coastal, mid-elevation regions

The same results were not found in coastal and mid-elevation regions, indicating they chose nonviolent solutions to climate change or were not affected by it, researchers said. There was also more agricultural and economic diversity there, potentially buffering against the onset of climate change. Drought-induced resource scarcity in the highlands, however, seems like a likely explanation for the violence there, researchers said.

Snyder said looking at the history of people’s interaction with nature is important when considering possible effects of current climate change challenges and people’s interaction with their climate.

“Our findings reinforce the idea that people living in already marginal environments are the most likely to be hit hardest by climate change,” he said. “Archaeological research can help us predict how best to handle the challenges faced by people in precarious positions in a rapidly changing climate.”

UC Davis researchers recorded violence during early years in the Andes by analyzing existing data of nearly 3,000 skeletal fractures of humans found at 58 archaeological sites — comparing them to ice accumulation at the time at the Quelccaya glacier — in what is now Peru, Chile and Bolivia. At the same time, there was widespread abandonment of Wari and Tiwanaku sites in the region, indicating a sociopolitical unraveling after the onset of the centuries-long global climate changes.

The archaeology of the Andes provides an excellent opportunity to study the human response to climate change given the region’s extreme climatic variability, incredible archaeological preservation and robust records, researchers said. In this study, researchers found that on average, for every 10-centimeter decrease in annual ice accumulation at the Quelccaya glacier, the likelihood of interpersonal violence more than doubled.

In multiple sclerosis, inflammation spurs the immune system to strip away the protective myelin coating around nerve fibers in the brain’s cortex, hampering electrical signals sent and received by the brain. Atrophy of the cortex in MS patients is associated with permanent worsening of disability, such as cognitive decline, visual impairment, weakness and sensory loss.

No currently available treatments for MS can repair damage to myelin. Instead, these treatments target inflammation to reduce symptom flare-ups and new nerve tissue scarring. Previous UCLA-led research found that estriol, a type of estrogen hormone produced in pregnancy, reduced brain atrophy and improved cognitive function in MS patients.

In the new study, researchers treated a mouse model of MS with estriol and found that it prevented brain atrophy and induced remyelination in the cortex, indicating that the treatment can repair damage caused by MS, rather than just slow the destruction of myelin.

This is the first study to identify a treatment that could repair myelin in the cortex, undoing some of the damage caused by MS.

Allan MacKenzie-Graham, an associate professor of neurology, is the study’s corresponding author. Other authors include Cassandra Meyer, Andrew Smith, Aitana A. Padilla-Requerey, Vista Farkhondeh, Noriko Itoh, Yuichiro Itoh, Josephine Gao, Patrick Herbig, Quynhanh Nguyen, Katelyn Ngo, Mandavi Oberoi, Prabha Siddarth and Rhonda R. Voskuhl, all of UCLA.