The study is looking to balance farmers’ sustainable management practices while improving their overall crop productivity

By BRANDON NGUYEN –– science@theaggie.org

Amid the unpredictable impacts of climate change, UC Davis has been recently awarded $10 million in grant funding by the U.S. Department of Agriculture’s National Institute of Food and Agriculture. Researchers from a wide range of fields — from socioeconomics to agricultural groundwater and soil health — will collaborate to optimize groundwater and agricultural irrigation sustainability in the Southwest for farmers to improve crop yield and cost efficiency.

Isaya Kisekka, an associate professor of agrohydrology and irrigation at UC Davis, will be leading a massive collaborative study with a team of researchers from California, Arizona and New Mexico to develop climate adaptation strategies that effectively sustain groundwater quantity and quality as well as irrigated agriculture.

Kisekka introduced the climate issue that the study tackles and the limitations that farmers currently face.

“In California, we are always experiencing droughts and floods, the climate extremes,” Kisekka said. “During the drought, farmers typically rely on groundwater or in the past, they have relied on groundwater until 2014 when Gov. Brown passed a new law called the Sustainable Groundwater Management Act that limited how much water would be pumped in from groundwater. And so, if growers cannot pump groundwater during periods of severe drought, what can they do?”

Depleting and overdrafting groundwater can have serious consequences, leading to groundwater deterioration and land subsidence where the land starts to sink, affecting infrastructure like roads and canals. Kisekka and his team understand that many communities’ economies depend on irrigated agriculture, so balancing sustainability and production is the goal of the study.

“Growers have increasingly depended on groundwater during multi-year droughts and heat stress,” according to a recent UC Davis press release. “Part of the five-year project includes looking into aquifer systems in California’s Central Valley, central Arizona and the lower Rio Grande basin in New Mexico. These regions have all experienced unprecedented overdraft, which happens when more water is pumped from a groundwater basin than is replaced from sources, including rainfall.”

California is the largest agricultural state in the country, with agricultural receipts exceeding $50 billion, according to Kisekka.

“California’s agricultural sector is a huge industry,” Kisekka said. “But that industry relies heavily on water, because we are in semi-arid climates, with many growing areas having the Mediterranean climate where you don’t get a lot of rain during the summer.”

Iael Hoffmann, a postdoctoral at Kisekka’s lab studying agricultural water and nitrogen management, provided insight into how she is contributing to the study’s development of agricultural management strategies through her project in the Central Valley.

“We are looking into how management practices like processing tomato rotation fields affects groundwater quality,” Hoffman said. “So we’re measuring irrigation, water and nitrogen balances, but at the field scale, at soil scale and also at the groundwater scale. So we’re monitoring these three levels.”

The core of Kisekka’s project is the development of better data and tools for farmers to optimize their growing practices toward more sustainable groundwater and irrigated agriculture. Kisekka provided examples of what his team of researchers plan to do for long-term sustainability of groundwater.

“One of the things we’ll be doing is managing aquifer recharge, where during a drought, we flood agriculture fields and make the water salt into the ground to recharge groundwater, which can be topped during the dry periods,” Kisekka said. “We are also developing best management practices on soil health, for example, using cover crops and other soil amendments to increase the ability of the soil to store water, also to make the crops more resilient either during a heatwave or severe drought. We’re also looking at smart technologies, like remote sensing and artificial intelligence so growers can start to use data to optimize decision making.”

These are just a few of the many potential management practices Kisekka and his team will be working on for farmers to best optimize their growing practices while sustaining groundwater under the limitations of the Sustainable Groundwater Management Act.

The future of agricultural practices is evolving, and Kisekka commented on what changes will need to be made to adapt to the constantly changing climate.

“Agricultural practices will have to be smart,” Kisekka said. “In some ways, it may be a smaller footprint, but more intensified. So you’ll have sustainable intensification of already very intensive systems. Instead of expanding the number of acres we are growing, we may cap or even decline a little bit, but productivity will increase. And [there] will be more use of data to make decisions and technology in general.”

Written by: Brandon Nguyen — science@theaggie.org

Utilizing chemistry, physics, materials science and artificial intelligence, the research will model and synthesize new clathrate structures with a wide array of potential applications

By SONORA SLATER — science@theaggie.org

Researchers at UC Davis and Iowa State University recently received a $700,000 grant from the U.S. Department of Energy (DOE) to discover and synthesize new clathrates, according to a recent press release. Clathrates are a chemical crystal structure that are known for their cage-like frame. The word ‘clathrate’ comes from the latin word Clathratus meaning ‘with bars,’ or ‘latticed. The researchers aim to explore potential applications of the materials, from better cooling for computers and cars to renewable energy options, as well as simply the base rules that define clathrate structures and properties.

Davide Donadio, an associate professor in the Department of Chemistry at UC Davis and the principal investigator for the project, explained that clathrate crystals consist of two parts: a frame that forms the titular “cages,” and the “guest atoms” that reside within the cages.

The physical properties of the clathrates change depending on the atoms forming the cage structure and the guest atoms trapped within. They can exist naturally, as in water and methane, as well as through synthesis in labs.

“You have so many ways of designing these materials, from a chemical standpoint, to achieve different properties — the chemical space is pretty wide,” Donadio said. “You have to satisfy some chemical rules, you need to form covalent bonds, but there are a lot of possible realizations.”

Specifically, Donadio and Kirill Kovnir, an associate professor of chemistry at Iowa State University partnering with Donadio, will seek to synthesize clathrates built from type III-V and II-VI atoms, with alkaline-earth metal atoms in the cages. But according to Donadio, there’s lots of theoretical modeling that goes on before any clathrates are synthesized.

“My work is theoretical, and I think one of the strengths of this proposal is that my theoretical work is intertwined with experimental work by Kirill,” Donadio said. “So my group will set up a model to predict the stability of clathrates with a given chemical composition.”

Donadio elaborated, saying that they do this by modeling the interaction among the atoms a material is composed of in different ways depending on the properties they want to look at — things like if it’s a semiconductor, the stability it’ll have, the vibrations of the particles and so on. However, doing these calculations can be very time consuming and computationally expensive.

“Doing calculations to determine properties […] a simple material goes pretty fast, I can do it on my laptop,” Donadio said. “But when I start to simulate a more complex material like these clathrates, some of these have like 260 atoms, or a multiple of those, so machine learning is a way of speeding up complex calculations.”

According to Donadio, machine learning allows them to train a machine based on known calculations, to be able to predict the properties of new structures without going through all of the electronic structure calculations.

Zekun Chen, a third-year Ph.D. student in the chemistry department at UC Davis working for Donadio, and a machine learning expert, discussed the role machine learning has played in clathrate research.

“Machine learning is keen at inferring structure-property relations from the trend of known data,” Chen said via email. “Our goal is to build predictive machine learning models based on available data of thousands of known compounds. [We can then] apply them to make predictions on renovative clathrate materials.”

Chen went on to explain the value of these predictions.

“These predictions are important because they can help us understand the fundamental principles of this group of clathrates,” Chen said via email. “Meanwhile, once sufficiently developed, this machine learning workflow can be extendable to study other classes of materials. Thus, machine learning can be helpful in material discovery in general.”

Donadio said that synthetic clathrates have been around for a while, but in a limited way, with most of the frames being made out of silicone, carbon, germanium and tin — all in the same column of the periodic table. But Kirill’s experimental efforts allowed him to synthesize clathrates with different elements, opening up the path to future research with a more diverse array of clathrates.

These new clathrates, if successfully synthesized, have many possible future applications, including in the field of energy through thermoelectric energy conversion.

According to the press release about the grant, thermoelectric materials can both “offer a fix for overheating” by transferring excess heat away from electronics and convert heat into electricity.

Susan Kauzlarich, a distinguished professor in the Department of Chemistry at UC Davis who does experimental research centered around new thermoelectric materials, said that this works through what’s called “temperature gradients.”

“You have temperature gradients everywhere — the difference in temperature between the air and your skin, that’s a gradient,” Kauzlarich said. “You can use a temperature gradient to create electricity because the carriers, which are electrons, carry heat, and move from a ‘hot side’ to a ‘cold side,’ and that’s how electrical current is generated.”

According to Kauzlarich, thermoelectric materials can convert a temperature gradient into electricity, or an electrical current can be put into those materials and they will generate a temperature gradient.

She went on to explain how clathrates are involved in the conversation and research around thermoelectrics.

“For a really good thermoelectric material, you have to maintain a temperature gradient, so you want something that does not conduct heat very well,” Kauzlarich said. “And that’s what clathrates do in general; many clathrates don’t conduct heat very well.”

Donadio went on to say that apart from thermoelectrics, there are also applications in batteries to make solid-state electrolytes to replace current plastics, for the sake of safety and efficiency. However, he said that application is not their project’s main goal — rather, they’re simply seeking to discover what clathrates can be synthesized, and what chemical rules define their stability and properties.

“We want to explore the chemical space to find new clathrates with possibly unprecedented properties,” Donadio said. “[…] If we find something with very low thermal conductivity and decent electronic properties, then it could be a good candidate for thermoelectrics, but we’re not focusing on that.”

Donadio and Kovnir’s research is inherently interdisciplinary, and Donadio described how that has been essential to the project.

“The research we do in my group is really across the boundary of chemistry, physics, and materials science,” Donadio said. “We are using methods that have been developed by physicists, and we are applying them to a chemical problem. On top of that, we have all this new artificial intelligence that really plays an important role in this project.”

Kauzlarich emphasized the support the chemistry department has for Donadio’s research and the potential of new discoveries.

“We’re all very excited […], and I know that he’ll make great progress looking at these, because again, there’s so many different combinations that you can have, and finding the best ones is like finding a needle in the haystack,” Kauzlarich said. “So I’m sure that his contributions to the area will help experimentalists everywhere.”

Written by: Sonora Slater — science@theaggie.org

UC Davis Center for Neuroscience explores potential clinical application to Alzheimer’s disease

By AARYA GUPTA — science@theaggie.org

UC Davis researchers from the Center for Neuroscience conducted a brain imaging study exploring the role of the hippocampus in linking separate events into a single narrative. This paper was published in Current Biology.

Neuroscience M.D-Ph. D. student Brendan Cohn-Sheehy said via email that the hippocampus plays an important role in episodic memory, which is “our ability to form and then retrieve memories that are linked to specific times.”

“We’ve known for some time that the hippocampus can form memories for specific events, that is, information that takes place during a specific period of time,” Cohn-Sheehy said. “But we got to thinking that to some degree, that isn’t the full story.”

Researchers began pondering why it would be beneficial to keep all life events separated in our memory, Cohn-Sheehy said.

Dr. Charan Ranganath, professor of psychology and head of the Dynamic Memory Lab, said that at the crux of this research lies the following question: how is information put together in memory?

“We actually wrote and recorded some short audio stories which served as our experimental stimulus, which was a pretty fun task,” Cohn-Sheehy said.

For example, participants might have listened to a fictional story about Charles, a photojournalist trying to get his big break. However, the participants were unaware that the experimental conditions actually involved the side-characters that were mentioned in the story.

“It’s kind of like when a side-character in a sitcom […] shows up at a couple different points in a TV show, and although their appearances are separated, they might form one larger narrative,” Cohn-Sheehy said. “We did the same thing in our stories […] Side-characters would show up in separated events that were unrelated to the surrounding stories, and which could either form one larger narrative or not.”

To collect data, researchers used magnetic resonance imaging, or MRI, to scan the participants’ brains on the day they listened to the stories and on the subsequent day, when participants were expected to recall every detail they could remember.

“[W]e analyzed brain activity by isolating the unique map of activity in the hippocampus at any given point in time and how similar this pattern was between events that formed one narrative, versus events that did not,” Cohn-Sheehy said.

Cohn-Sheehy emphasized that the pattern similarity informs researchers about how much the hippocampus supported information that could link separate events into a narrative.

The idea that separate memories are created by the hippocampus for different

experiences had by an individual is emphasized across many theories in neuroscience, Ranganath said via email. However, according to him, humans intuitively violate this idea, drawing light to the hippocampus.

“[W]hen we recall information from the past, we often put together information from separate events into a seamless narrative,” Ranganath said. “For instance, if you ran into a friend walking into a sketchy restaurant and later that day she complains that she got food poisoning, you would be likely to put that information together into a single narrative.”

Researchers hypothesized that the hippocampus may be responsible for forming linkages between information from the past with information in the present to build narratives.

“We found that when people were listening to events in these stories, when two of these side-character events could form one larger narrative, the hippocampus had more similar patterns of activity between those two events, compared to two side-character events which could not form one larger narrative,” Cohn-Sheehy said.

The results also have built on previous behavioral studies.

“One application of this research is that it helps us take what we know about memory into the real world,” Ranganath said.

Cohn-Sheehy agreed, adding that there is a potential clinical application.

“This research was done in healthy young adults,” Cohn-Sheehy said. “But we want to see whether similar effects carry to older adults, that is, do narratives play the same role in real-life memory across the lifespan […] If we build on research like this to develop more realistic, sensitive memory tests, maybe we’ll be able to develop better early screening tests for Alzheimer’s and other memory disorders.”

Ranganath further explained that this study explores the role of narratives in near-life memory by using a task that tests memory in a way that mimics how humans recall events in the real world.

“For instance, most adults over the age of 50, unlike college students, don’t spend their days studying meaningless information in anticipation of a test,” Ranganath said. “When older adults do badly on a memory test, we don’t know if that is because they have a memory problem or that they are just bad test takers.”

Undergraduate research assistants were integral to this project, Cohn-Sheehy said.

“We had undergraduate research assistants who were blinded to the study hypotheses and conditions score how many details participants remembered,” Cohn-Sheehy said.

Cohn-Sheehy encourages students to get involved.

“As a Neurobiology, Physiology and Behavior major, I learn a lot about biological and chemical principles in my classes,” third year Tyler Cunningham said. “Research like this excites me because I get to learn more about the mechanisms behind these principles and then see their application to help solve-real world problems.”

This research involves cognitive neuroscience, a field that explores how humans experience the world around us and how our brain supports that, according to Cohn-Sheehy.

Written by: Aarya Gupta — science@theaggie.org