“There’s a beautiful interplay between pure mathematics and materials science,” says Greg Grason, the paper’s senior author and a professor of polymer science and engineering at UMass Amherst. “Our work investigates how materials self-assemble into natural forms.”

These forms can take many shapes. They can be simple, like a layer, cylinder or sphere. “A bit like soap films,” adds Michael Dimitriyev, a postdoctoral researcher in polymer science and engineering at UMass Amherst, and one of the paper’s co-authors. “There’s an intuitive understanding of the shapes that molecules, such as those in soap, can build. What we’ve done is to reveal the hidden geometry that allows polymers to assume the double-gyroid form.”

What does a double-gyroid look like? It’s not intuitive. “They’re something in between a layer and a cylinder,” says Abhiram Reddy, a postdoctoral researcher at Northwestern who completed this research as part of his graduate study at UMass Amherst and the paper’s lead author. In other words, imagine a flat piece of window screen — a layer — and then twist it up into a saddle-shaped layer that fits into a cubic box in such a way that its surface area stays as small as possible. That’s a gyroid. A double-gyroid is when a second material, also twisted into a gyroid, fills in the gaps in the first gyroid. Each gyroidal material forms a network of tubes that interpenetrates the other. Together, they form an enormously complex material that is both symmetrical on all sides, like many crystals, yet pervaded by labyrinthine channels, each formed from different molecular units. Because this material is a hybrid of two gyroids, it can be engineered to have contradictory properties.

These double-gyroids exist in nature and have long been observed, but until now, no one has quite figured out how chain molecules, known as block copolymers, know how to form double-gyroids. Reddy and his co-authors built upon a previous theoretical model, adding a heavy dose of thermodynamics and a new approach to thinking about the packing problem — or how best to fill a finite container with material — borrowed from computational geometry and known as the medial map. Since the copolymers need to stretch to occupy every part of the self-assembled structure, understanding this formation requires knowing how the molecules “measure the middle” of shapes, like gyroids, that are far more complex than spheres and cylinders. The team’s updated theoretical model not only explains the puzzling formation of double-gyroids but holds promise for understanding how the packing problem works in a much broader array of self-assembled superstructures, such as double-diamonds and double-primitives, or even structures that have yet to be discovered.

The researchers, who were funded by the US Department of Energy, next plan to collaborate with synthetic chemists to begin refining their theory with experimental data. The end goal is to be able to engineer a wide variety of materials, which take advantage of the double-gyroid’s structure and that can help advance a wide range of technologies from rechargeable batteries to light-reflecting coatings.

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Targeting these cells, as reported in the journal Nature Neuroscience, modulated memory retrieval and altered anxiety-like behaviors in mice. Essentially, the UNC scientists boosted the electrical activity between cells in the hypothalamus and the hippocampus to create new neurons — an important process called neurogenesis.

“Targeting the hypothalamic neurons to enhance adult hippocampal neurogenesis will not only benefit brain functions,” said senior author Juan Song, PhD, associate professor of pharmacology, “but also holds the potential to treat cognitive and affective deficits associated with various brain disorders.”

Most neurons we carry for life were created before we were born and get organized during early childhood. But such neurogenesis continues into adulthood and throughout life. In fact, one of the reasons for cognitive decline and anxiety, and even diseases such as Alzheimer’s, is the suspension of neurogenesis.

Song, a member of the UNC Neuroscience Center, has been studying the detailed interplay between brain cells that keep neurogenesis chugging along. She knew that adult hippocampal neurogenesis plays a critical role in memory and emotion processing, and that neural circuit activity — think ‘electrical activity’ — regulates this process in a constantly changing manner.

What no one knew is whether this neural circuit activity could be manipulated to spur neurogenesis to such a degree that the effect would be seen as a changed behavior, such as better memory or less anxiety.

To see the effect of modulating neural activity, the Song lab conducted experiments led by co-first authors Ya-Dong Li, PhD, and Yan-Jia Luo, PhD, both postdoctoral fellows. They used optogenetics — essentially a method using light to trigger neuronal activity — in a small brain structure called supramammillary nucleus (SuM). The SuM is located inside the hypothalamus region of the brain; it helps manage things from cognition to locomotion and sleep/wakefulness.

When Song’s researchers chronically stimulated the SuM neurons, they discovered a robust promotion of neurogenesis at multiple stages. They observed increased production of neural stem cells and the creation of new adult-born neurons with enhanced properties. Optogenetic stimulation of these new neurons then altered memory and anxiety-like behaviors.

“We also show that the SuM neurons are highly responsive when the mice experienced new things in their environment,” Song said. “In fact, in a new environment, mice require these cells for neurogenesis.”

Impaired adult hippocampal neurogenesis correlates with many pathological states, such as aging, neurodegenerative diseases, and mental disorders. “Therefore,” Song added, “targeting the hypothalamic neurons to enhance adult hippocampal neurogenesis will not only benefit brain functions but also holds the potential to treat cognitive and affective deficits associated with various brain disorders.”

Other authors are Ze-Ka Chen, Luis Quintanilla, and Libo Zhang at UNC-Chapel Hill; Yoan Cherasse and Michael Lazarus at University of Tsukuba, Japan,; and Zhi-Li Huang from Fudan University, China.

This research was funded through National Institutes of Health, the Alzheimer’s Association, and NARSAD Young Investigator Award from the Brain & Behavior Research Foundation.

The study consists of 120,000-plus images taken in eight countries, representing the largest photo database to date of the Amazon’s staggering array of wildlife. The images show 289 species taken from 2001-2020 from 143 field sites.

The WCS images from Bolivia, Brazil, Colombia, Ecuador and Peru reveal playful jaguar cubs, a giant anteater lounging in a mud wallow, elusive short-eared dogs, along with tapirs, white-lipped peccaries, harpy eagles, toucans, pumas, Andean bears and dozens of other species. Jaguars and Andean bears are priority species for WCS.

The purpose of the study is to build a database of Amazon wildlife images, while also documenting habitat loss, fragmentation and climate change. The Amazon Basin covers nearly 3.2 million square miles (8.5 million square kilometers) in Brazil, Bolivia, Colombia, Ecuador, French Guiana, Peru, Suriname and Venezuela.

Said Robert Wallace, Director of WCS’s Greater Madidi-Tambopata Landscape Program, and a co-author of the study: “WCS scientists were proud to collaborate with such a diverse group of scientists and organizations on this important study. The tens of thousands of images WCS provided will serve as critical data points to show where wildlife occurs and the staggering diversity of species found in the Amazon region.”

One hundred forty-seven scientists from 122 research institutions and nature conservation organizations collaborated on the Ecology study, which was led by German Centre for Integrative Biodiversity Research (iDiv) and the Friedrich Schiller University Jena.

This study marks the first time images from camera traps from different regions of the Amazon have been compiled and standardized on such a large scale.

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