November 2017

Investment Portfolio Theory Helps Scientists Predict Animal Population Growth, Disease Spread

A new study published in PNAS details a new “landscape portfolio” theory that uses insights from economics to predict animal population growth and the spread of disease.

The paper, co-authored by Stony Brook’s Jessica Gurevitch, PhD, a Professor in the Department of Ecology and Evolution in the College of Arts and Sciences, melds Harry Markowitz’s “portfolio theory” in economics with ecological landscape theory to predict population growth of living things.

Population demography of plants, animals and microbes that cause diseases is central to understanding many problems in ecology, evolution and conservation biology. Scientists have had limited information on collections of living populations to understand and predict what happens when you have many populations spread across vast geographic areas. Most research has focused only on local populations at small scales.

Co-author Jessica Gurevitch, PhD, a Professor in the Department of Ecology and Evolution in the Stony Brook University College of Arts and Sciences, and colleagues discovered by using this landscape portfolio theory – verified with data on gypsy moth populations – something surprising occurs: When groups of populations are assessed over a large area, the total numbers of all of them together can grow even when none of the individual populations are growing. This is called “growth inflation” – a concept similar to diversified financial investing and total investment growth.

When growth inflation happens with living populations, the risk of population volatility or plummeting population numbers becomes very small. Synchronicity among the populations was key to their discovery.

“This theory incorporates new developments based on the relationships among populations, which can potentially help scientists better predict geographically widespread growth of populations,” said Professor Gurevitch. “The theory can also offer new insights to growth in fields as diverse as medicine and economics.”

Co-authors of the paper include Cang Hui from the Stellenbosch University, South Africa and Gordon Fox, from the University of South Florida.

Caribbean Islands Reveal a “Lost Word” of Ancient Mammals

Although filled with tropical life today, the Caribbean islands have been a hotspot of mammal extinction since the end of the last glaciation, some 12,000 years ago. Since people also arrived after that time, it has been impossible to determine whether natural changes or human influence are most responsible for these extinctions.

The “lost world” of Caribbean animals included ground sloths, enigmatic monkeys, giant rodents, a vampire bat, and shew-like insectivores before the arrival of humans. (Illustration by D. Rini.)

A new study by an international team of scientists, including Stony Brook University Professor Liliana M. Dávalos, reports an analysis of the incredibly diverse “lost world” of Caribbean fossils that includes giant rodents, vampire bats, enigmatic monkeys, ground sloths, shrews and dozens of other ancient mammals. The study, published today in the Annual Review of Ecology, Evolution, and Systematics, reveals that the arrival of humans and their subsequent activities throughout the islands was likely the primary cause of the extinction of native mammal species there.

The Caribbean islands were not the only region to lose many mammal species; many large mammals from ground sloths to mastodons also vanished from continental North America. As dramatic and natural changes in the environment and the arrival of people to the continent roughly coincide in time, a scientific debate on what caused the demise of this fauna continues. Because people arrived to the islands long after the end of the glaciation, starting some 6,000 years ago, the Caribbean islands provide an ideal laboratory for discovering the cause of these losses.

In the paper, the scientists report analyses of the most comprehensive radiocarbon data set of Caribbean mammals and human arrivals in the Caribbean, representing 57 extinction and extirpation (when a population vanishes from an island) events for native species. While the scattered data by themselves are invaluable, separate data points are hard to interpret, as different methods used at various sites can obscure larger patterns. So, the research team introduced a chronology developed by collecting established fossil dates reported in dozens of already-published and peer reviewed papers in an array of scientific journals.

“By using models to estimate the time of overlap between people and extinct mammals on each island, we were able to show most mammal extinctions happened after the arrival of humans on various islands in the Caribbean, and not before,” explained Dávalos, who led the quantitative analyses of the study. While the overlap between people and the fauna is not proof positive of human causes for the many extinction events in the region, it is an important step to determine why these mammals went extinct. Weaving together data from the many journal articles and archaeological site reports, the team concluded that the timing of extinctions indicates humans may be involved in the extinction of more than 60% of the nearly 150 native mammal species.

Multiple waves of human settlement in the Caribbean occurred over the past six to seven thousand years. The first settlers, Amerindian people from South or Central America known as the Lithic culture, were followed by two other waves – the Archaic and Ceramic, both from South America. The authors showed that after the initial waves of human arrival, mammal extinctions followed, presumably first caused by hunting and later by forest clearing for agriculture, which reduces the habitat for native mammals. A final wave of human migration, this time from across the Atlantic, brought with it cats, rats, goats, mongoose, and other introduced mammals. The ensuing change in habitats, and both competition and predation, resulted in the extinction of about a dozen populations on the smaller islands of the Lesser Antilles. These predators and competitors can affect the populations of Caribbean mammals that survived previous extinction waves.

“While this paper is the result of an important collaboration of scientists – with each author bringing their expertise to the table to solve the puzzle mammal extinction – saving the community of mammals of today needs a much wider group of professionals, especially on each island, which is why we are assembling a larger team,” she added.

Dávalos’ team is now working to bring together a larger, interdisciplinary team of colleagues to create an intensive conservation management plan incorporating the expertise of conservation researchers, biologist, ecologists, policy-makers, educators, and land and wildlife management experts to save the last surviving native Caribbean mammals.

“In examining data from both paleontological digs and archeological reports, the evidence highlights the need for urgent human intervention to protect the native mammal species still inhabiting the region, and that is why we are coming together with scientists from all over the Caribbean,” concluded Dávalos.

The study was funded in part by the National Science Foundation.

Materials Science and Engineering Professor Uses Art to Communicate Science

The study of objects less than a billionth of a meter, also known as “nanometers,” is a special research discipline that Materials Science and Engineering Professor Alexander Orlov has been working on for years. A major breakthrough in this field has been the emergence of a new generation of consumer products containing nanoparticles, nano-enabled biomedical devices and many other exciting developments straight out of science fiction novels. However, like many scientific breakthroughs, there is hesitation in the implementation of nanotechnology.

 

Professor Alexander Orlov and student Marija Iloska use nanoart to visualize nanotechnology.

“It is a very difficult area to describe, as you cannot see nanoparticles with the naked eye,” Orlov explained. “People fear nanotechnology similar to radiation.”

To help the general public understand and accept this new technology, Orlov began using nanoart to visualize nanotechnology. He teamed up with Marija Iloska, a student studying chemical and molecular engineering in the College of Engineering and Applied Sciences, to infuse colors into the black-and-white nano-objects.

Iloska has been drawing and painting since she was a young girl in Macedonia, but compared to drawing portraits and landscapes with colored pencils, she says that coloring nano-objects is a whole different ball game.

“It is very interesting because there are really no limits to the imagination. It’s like opening your mind to see other things,” said Iloska. “I combine colors that go together to make the best impression with what I am trying to illustrate.”

Yet finding that balance between art and science is not always easy. Orlov says that nanoart adds color and dimension to attract public interest and attention in the science, but those colored images reduce accuracy and precision.

“It is sort of a compromise,” Orlov explained. “If the public can understand what it’s about, accuracy isn’t the highest priority,” he said. With a suitable amount of color and a little bit of imagination, nanoart can help share some of the scientific breakthroughs material scientists like Professor Orlov are pioneering.

In his recent research, Orlov discovered the use of concrete to eliminate harmful air pollutants, including sulfur and nitrogen dioxide, and minimize air pollution. With the help of Iloska, he presented research findings using a colored electron microscopy image of sulfur dioxide interacting with concrete.

“Our research has real applications but what we are also trying to do, in terms of outreach and perception, is bring it to life in colors,” said Orlov. “When we are working with the chemical benefits of concrete, a little color can go a long way.”

— Kristie Kam

Sandhu Wins Air Force Grant for Bridging the Information Gap

For his work focusing on the risks involved in deploying fully autonomous computer systems, Romeil Sandhu has been awarded $450K from the Air Force Office of Scientific Research (AFOSR), through the Air Force’s Young Investigator Research Program.

Sandhu is an assistant professor in the Department of Biomedical Informatics, jointly administered by Stony Brook’s College of Engineering and Applied Sciences and School of Medicine. His research could impact autonomous systems for a variety of systems that rely on artificial Intelligence, including self-driving automobiles and drones.

Professor Sandhu is one of only 43 scientists and engineers to receive the award, for his proposal addressing 3D Interactive Feedback Control for Autonomous 2D Imaging Systems.

AFOSR received more than 285 proposals for this prestigious early career award, open to scientists and engineers at research institutions across the United States who received PhD or equivalent degrees in the last five years. The program’s objective is to foster creative basic research in science and engineering, enhance early career development of outstanding young investigators, and increase opportunities for the young investigators to recognize the Air Force mission and the related challenges in science and engineering.

“Rome is a brilliant young faculty with tremendous mathematical talent,” said Joel Saltz, MD, Chair of the Department of Biomedical Informatics. “I am extremely excited about this well-deserved award which will allow him to continue to generate groundbreaking new results.”

Sandhu’s research is focused on developing models and theory for understanding dynamical systems through the confluence of discrete geometry, statistics, and control spanning topics ranging from network science, computational vision, systems biology, and machine learning.  In particular, the AFSOR awarded Sandhu’s work in combating risk complexities we face in the real world when deploying autonomous systems such as unmanned (driverless) vehicles.

“Today, there is no universal machine learning algorithm capable of handling all real-world scenarios, so we often require humans to ‘interact’ with these systems to deal with the ‘unknown unknown.’  Whether it is protecting the soldier in the field, performing situational awareness, or self-driving cars, we have not reached a point in which we can trust complete autonomy over basic human input,” Sandhu said.

“Artificial Intelligence is a strategic research thrust for our college.  Rome’s research will lead to breakthroughs that will enable humans to better interface with intelligent systems and will impact a wide range of AI-driven technologies,” said Fotis Sotiropoulos, Dean of the College of Engineering and Applied Sciences. “This prestigious award is a major career accomplishment for Rome  and I am really proud to have faculty of his caliber in our college.”

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