Researchers learn more about properties of light-distorting dark matter particles

For a substance that makes up approximately 27% of the universe, there is surprisingly little knowledge about dark matter. Despite not actually detecting a dark matter particle yet, we know that dark matter exists because its existence is necessary for galaxies to hold themselves together gravitationally. We also know that dark matter distorts light from distant celestial objects, and this is the property that Chris Fassnacht, a physics professor at UC Davis, and his team utilized to study the substance. 

“I have been using gravitational lensing and high-resolution imaging (where you can see many small details) for over 20 years to learn about the properties of the Universe,” Fassnacht said, via email. “About 10 years ago, I started taking advantage of the new ‘adaptive optics’ technology that allows the Keck Telescopes to correct for the blurring effect of the Earth’s atmosphere to get really detailed images of gravitational lenses.”

Gravitational lensing is a non-traditional method of testing theories surrounding dark matter. It is the distortion or bending of light by distant objects as it passes by massive celestial objects. 

The standard model of dark matter assumes it to be ‘cold’ and thus have particles that move slowly in comparison to light. A warm model, however, has been proposed that explains the difference between what the cold model predicts and what observations reflect. 

“The goal was to see what limits can be set on the ‘temperature’ of dark matter,” said Leon Koopmans, a professor at Kapteyn Astronomical Institute, via email. “Warm dark matter clumps less and gives fewer or smaller anomalies in lensed images. Since we do see some anomalies, we can set limits on how warm dark matter can be (if it’s too warm, we would never see anomaly).”

This study looks mainly at flux-ratio anomalies, although “surface brightness anomalies” are also examined via techniques like gravitational imaging to provide insight into the temperature and corresponding behavior of dark matter. 

Former UC Davis postdoc John Mckean — now a professor at Kapteyn Astronomical Institute — was working with Fassnacht on the observation of gravitational lenses using the Keck Telescope in Hawaii. His goal was to identify companion, or satellite, galaxies to mainland galaxies to understand the overall mass distribution of the lenses. 

“[What is expected] is that the dark matter is quite smoothly distributed throughout the entire halo but if the dark matter is clumpy, that causes an aberration in the lens which causes the images to look different from what we’d expect in the case of a smooth model,” Mckean said. “What we are trying to do is to look for small differences between what we’d expect from clumpy or a smooth lens galaxy where the clumpiness tells us that dark matter is more consistent with the cold model. Or, if the clumpiness is quite low and the halo is quite smooth we think that is more consistent with what we call a warm dark matter particle.”

The hope is that this study will help narrow down the definition of dark matter, making it easier to identify. This research increases constraints on the nature of dark matter, laying the groundwork for tighter constraints in the future. 

Written by: Husn Kharabanda — science@theaggie.org

Human development research focused on often overlooked communities 

In California, Hispanics have surpassed whites as the largest ethnic group in the state. Although it is often thought that this increase is due to immigration, it is actually caused by individuals already living in the state and building families. 

Hispanics increasingly choose to raise families in the U.S., yet little research has gone into understanding their family dynamics and childhood development. Instead, research in human development has historically been focused on white Americans of European descent, resulting in a lack of representative knowledge. Leah Hibel, an associate professor of human development and family studies, is striving to bridge this racial gap in scientific research and learn more about the lives of Hispanics in the U.S.

The California Babies Project began in 2017 with the intention of learning how stress factors impact childhood development in Mexican families in the Yolo County area. The project selected families that had already been studied through the California Families Project, a childhood development study that started at UC Davis in 2006. 

The children that are part of the ongoing California Babies Project are the descendants of those who participated in the 2006 California Families Project as children. Hibel’s study hopes to better understand the daily lives of the families through understanding the main stressors they are facing and the resilience mechanisms they rely on to combat challenges.

“The main goals of the project are to understand daily life as it’s lived, how parents are supporting their infants’ development and their infants’ ability to regulate their physiology, emotions and sleep” said Andrea C. Bühler-Wassman, a doctoral candidate in human development. 

To collect data on the families and children, the study started with children at six months old and plans to follow them until they reach the age of four. A key part of data collection relies on the diaries that the families use to document the many fluctuations in daily life during two-week periods.

“What is unique about this project is that we have the families filling out questionnaires each day, so we can see how life is lived each day and how each day is impactful,” Hibel said.

Beyond the daily diaries, a quantifiable aspect of the study is the recording of the stress hormone cortisol. To measure cortisol, saliva is collected from both the parents and the children. This physiological measure serves as an objective view of the parents’ stress levels and as an indicator for the way in which the parents’ stress is impacting their children. Additionally, sleep patterns are recorded to understand how differing amounts of sleep impact the health of the family members.

Although the study is still primarily in the data collection phase, early analysis has already identified stress factors and resilience methods among the families. Correlations can be found between partner hostility and the amount of sleep mothers receive each night. For mothers sleeping the recommended seven to eight hours a night, less partner conflicts are observed. These are experiences to which many families in the U.S. can relate; however, a specific stressor for the families in this study is the fear of deportation. 

The study has seen a significant difference in the depression symptoms for mothers who are worried about deportation compared to mothers with less concerns about deportation. Bühler-Wassman pointed out that it is not just undocumented mothers who are negatively impacted by the fear of deportation. Regardless of citizenship status, these mothers still have fears surrounding deportation — from concerns about other family members to racist assumptions that they might be undocumented — which may result in symptoms of depression. 

In the face of these stress factors, the families have shown strong resilience through familial support. The importance of family and the support members receive from one another helps them fight the challenges they face in the U.S. 

“We are currently studying how social support affects the families’ mental health, because when families are living in these stressful environments, the main thing that buffers that stress is familial support,” Bühler-Wassman said.

The researchers hope that more evidence-based research on Mexican families in the U.S. will ultimately lead to positive changes and more enjoyable lives for the families they study.

“I really want to make this research be reflective of the needs of the community and I hope that this research will be able to help them and give back to them,” Bühler-Wassman said. 

To help the families, policy and social services need to be catered to their specific needs. It is important for the societal support to be inclusive of all family types. This research will help policy-makers come up with specific solutions that will be most beneficial to the families they hope to serve. 

“It’s important to meet families where they are at and be able to provide families with prevention and intervention,” Hibel said. “We need to make sure those interventions are culturally appropriate and need them to be able to fit into their day to day lives.”

Although there has been widespread objection to policies that are negatively impacting immigrants and their families, Jonathan Mulligan Sepúlveda, a staff attorney for the UC Davis Immigration Law Clinic, emphasized that such policies have been this way for years.

“There does seem to be significant push back that is saying this is extremely inhumane policy, yet it seems like policy has been this way for a long time,” Mulligan Sepúlveda said.

Hibel stressed that it is ultimately a societal limitation to not support all the diverse aspects and people of the U.S.

“What is important to recognize is that our country is diverse and our communities are diverse, and that diversity is an asset,” Hibel said. “If we are not supporting and acknowledging aspects of our society, it holds our society back.”

Written by: Alma Meckler-Pacheco — science@theaggie.org

From teaching to research projects, D-lab focuses on sustainability

When Dr. Kurt Kornbluth looks back on his time designing and building wheelchairs in Africa and Central America, he regards his work as only semi-successful. Although he built better wheelchairs, the project revealed an inherent flaw: He had not accounted for the societal changes that would be required to maintain the positive impact his work had made. Instead of getting discouraged, Kornbluth was inspired to integrate technology into society in a more meaningful way.

Kornbluth is now a professor in the department of biological and agricultural engineering as well as the founder and director of the UC Davis D-Lab. The D-Lab, founded in 2009, is Kornbluth’s realization of his goal. Kornbluth and his staff work with clients, both local and international, to develop low-cost, clean and efficient technologies that are uniquely situated within the client’s requirements and vision.

The D-Lab also maintains a strong educational component. D-Lab courses, typically offered quarterly, assemble cross-disciplinary student teams to create sustainable solutions for a real client, both in the planning and prototyping phases. The D-Lab teaches a methodology that guides students in research and integrates four lenses of sustainability: social, environmental, financial and technical.

Kornbluth’s courses are a type of research in and of themselves. Working with the dean of the College of Engineering, he is developing experimental courses for the Engineering Student Design Center and figuring out how to most effectively facilitate professional and hands-on learning experiences. Kornbluth developed these pilot courses over the past few years, with research focuses ranging from Zero Waste and Zero Net Energy to their latest collaboration: Art and Engineering.

  The Art and Engineering course is the conceptual brainchild of Kornbluth and Luke Turner, the exhibition manager at the Jan Shrem and Maria Manetti Shrem Museum of Art. Both Kornbluth and Turner aim to reconcile two disciplines that are often seen as being in diametric opposition.

  “Art foregrounds a dimension of criticality and social engagement that engineering projects do not necessarily require,” Turner said. “This art coefficient brings a surplus value to projects that engineers may not be trained to recognize or address.”

  Projects commissioned by the Manetti Shrem Exhibition Department focus on sustainable exhibition design and an increasing push toward accessibility. One student team is exploring the use of natural or biodegradable exhibition furniture materials and adaptable modular design to reduce waste of furniture that traditionally must be custom-made for each exhibit. 

Although the museum itself is designed to be highly accessible, students are also looking at how to make the exhibition experience for everyone. Possible directions include engineered pedestals that allow the artwork to be lowered, while keeping the piece out of harm’s way.

Another student is in the process of developing an “immersive tea lab experience” for the UC Davis Arboretum, using concepts of art, design and engineering to convert an RV into an accessible experience for all.

  The class also incorporates art theory into “traditional” D-Lab projects that involve both local and international solutions to sustainability issues. One of these clients is the Student Farm, for which the D-Lab is conceptualizing plans for an electric tractor that is both quieter and more efficient. International projects include sustainable logging and waste management systems in the Democratic Republic of the Congo and Burkina Faso, respectively.

  Outside of the course, the D-Lab plays a big role in the UC Davis zero net energy initiatives. Kornbluth is an author of “Big Idea: Sustainable Cities,” a plan wherein the UC Davis community serves as a microcosm of a city, and project-based student courses use sustainability research to solve campus energy problems.

  Although other renditions of the D-Lab exist, the agricultural and energy research underway at UC Davis offers an opportunity to develop and prototype systems that translate particularly well into the real world, especially in developing countries.

  Spring Quarter 2020 will see the continuation of the Art and Engineering course as “D-Lab II: Design, Build, and Test.” Students interested in the course or learning more about the D-Lab should reach out to the program manager, Abigail Edwards, at amedwards@ucdavis.edu. 

Written by: Kat Hanrahan — science@theaggie.org

Genetic variation across climates affects seed germination

Seeds may appear lifeless as they lay dormant in the soil, but inside each little capsule is a complex biochemical machine waiting for the right time to spring to life. A new study led by UC Davis researchers investigated how climate conditions may play a major role in regulating the timing of plant life cycles. 

The most critical first step in a plant’s life is germination is the process of a plant sprouting from a seed. For a baby seed, timing is everything. To maximize their chances of survival, seeds should germinate only when the environmental conditions are just right. 

“If they germinate when there is too little water around, or under the snow, or when there are too many competitors, the plant won’t be able to survive,” said Daniel Runcie, an assistant professor in the department of plant sciences, via email.

Germination depends on a number of factors, including internal genetic instructions. Variations in the delay of germination 1 gene, or DOG1, were previously known to regulate seed dormancy. Researchers hypothesized that DOG1 may also be responsible for seed responses to cold temperatures.

This study used a traditional model organism called Arabidopsis thaliana, which is a weedy, fast-growing plant in the mustard family also known as the thale cress. Although it is native to Europe and Asia, it has been introduced around the globe and grows in many different climates. It is also an annual plant, meaning its entire life cycle is contained within a single growing season. These plant characteristics — fast growth, a short life cycle and the ability to adapt to many climates — make its seeds the ideal model for this study.

“The germination characteristics of seeds vary in different parts of the world because they have been selected by different climates, so we used Arabidopsis thaliana seeds from across its native Eurasian range to investigate different germination responses,” said Alejandra Martínez-Berdeja, the study’s lead author and UC Davis postdoctoral scholar in the department of evolution and ecology.

Arabidopsis seeds were collected from different locations across Eurasia that represented a variety of local climates. The researchers brought seeds from over 500 distinct lineages back to the lab and subjected them to 13 different cold treatments. Exposing the seeds to different temperatures shows which environment each plant is best suited for.

“Cold treatments simulated different seasonal cold conditions including fall and spring experienced by seeds,” Martínez-Berdeja said.

The Arabidopsis seeds were removed from cold chambers and allowed to germinate, with a very diverse range of results. Germination varied along a gradient of climates, indicating that seeds are able to detect and respond to environmental cues like temperature.

In seeds from warmer climates in Western Europe, cold temperatures cause the seeds to stay dormant to outlast the winter and germinate when temperatures become favorable in spring, so the plant won’t freeze to death before it reproduces. In other plant lineages from colder climates like Scandinavia, cold temperatures actually induce germination so that plants will grow in winter when it is most advantageous in that area.

“That was the cool result of the study,” said Johanna Schmitt, a distinguished professor in the department of evolution and ecology, via email. “In some genetic lines, prolonged chilling induced secondary dormancy, but in other lines brief chilling actually induced germination [without] secondary dormancy. These strategies were associated with climate.”

Researchers found variations in the DOG1 gene that correlate with plants found in significantly different climates. Aside from its previously known role in controlling seed dormancy, these results now link alleles of DOG1 to certain climates.

“I think the most exciting result is finding that DOG1 — a gene that is already well-known to affect dormancy — really affects dormancy in multiple ways depending on what environment it ends up in,” Runcie said. “The effects of different alleles at the DOG1 gene depend on the environment.”

  With the discovery of the underlying genetic instructions for seed responses to climate comes further research questions. Although Arabidopsis thaliana is a simple model plant, farms that grow its relatives in the mustard family may also benefit from the results of this research.

“Arabidopsis thaliana is related to important crops such as mustard, cauliflower, broccoli and canola, so research findings can help understand the germination responses of other plants, including domesticated plants and other wild species,” Martínez-Berdeja said.

Understanding the mechanisms that influence germination times allows crop breeders and farmers to grow and harvest crops more efficiently. Maximizing germination rates not only helps farmers grow more plants with the same seed input, but also treating seeds before sowing helps the crops germinate at the same time and mature together as well.

“Germination — and particularly cold effects on germination — is very important in crops, as farmers need all plants to germinate at the same time,” Runcie said. “Better understanding the genes that control when seeds [choose] to [remain] dormant, and are thus more difficult to get to germinate, could help breeders develop varieties that germinate more consistently.”

Written by: Lauren Glevanik — science@theaggie.org