Bonding over bones, stones and beads

By Carol Clark

"I've really been into bones since I was little. I don't know why," says Emory University senior Alexandra Davis, an anthropology major. "Not fresh bodies, though. No soft tissues or blood. Just bones."

In fact, Davis loves bones so much that she was willing to spend seven weeks in Malawi with Emory anthropologist Jessica Thompson and four more of her students last summer, excavating bones and other artifacts in ancient hunter-gatherer sites, assisted by a team of locals.

Thompson will return to Malawi in July with another team of students to continue excavation of two sites that were started last summer. "We want to get into the deeper layers, because in both cases we did not come close to reaching the bottom of the sites," Thompson says. "Then, we want to find out how old they are."

Read more about the project.

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Have skull drill, will travel

'Dog-nition' research set for Science Friday

Come. Sit. Stay. And listen to Science Friday's interview at 3:30 pm E.T. today with Emory neuroscientist Gregory Berns, who is exploring the inner workings of the canine mind. Two of the questions the program plans to explore: Do dogs have a concept of time? And how do our furry companions make sense of the world?

You can tweet questions you'd like answered to @scifri. The radio program is based at WNYC Studios, distributed to public radio stations across the United States, and is also accessible online.

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Emory chemistry receives $7.5 million to lead fuel cell research

"A deeper understanding of electrochemical processes is important in the quest for more efficient, renewable forms of energy," says Emory physical chemist Tim Lian, shown in his lab. Photo by Stephen Nowland, Emory Photo/Video.

By Carol Clark

The U.S. Department of Defense awarded $7.5 million to Tianquan (Tim) Lian, professor of physical chemistry at Emory University, to lead an investigation of electrochemical processes underlying fuel-cell technology. The award comes through the DoD’s highly competitive Multidisciplinary University Research Initiative, or MURI. The program funds teams of investigators from more than one discipline to accelerate the research process.

“A deeper understanding of electrochemical processes is important in the quest for more efficient, renewable forms of energy,” Lian says. His lab develops sum-frequency generation spectroscopy to selectively probe reactions on the surface of an electrode. The technique can provide insights into the fundamental steps involved in energy generation, conversion and storage technologies — ranging from solar cells, to fuel cells and batteries.

Fuel cell electric vehicles use a fuel cell instead of a battery — or in combination with a battery — to generate electricity for power. While they have lower emissions and higher fuel-efficiency than internal-combustion engines, fuel cell vehicles are currently limited to lighter fuels, such as hydrogen.

The Air Force Office of Scientific Research accepted the MURI proposal from Lian, principal investigator of the project, and his colleagues from five other universities, including Yale, Cornell, Massachusetts Institute of Technology, the University of Pennsylvania and the University of Southern California. Together, the researchers encompass the disciplines of advanced spectroscopy, electrochemical mass spectroscopy and electrochemical theory to model, test and interpret reactions.

“Bringing together experimentalists and theorists with different backgrounds gives us the expertise to tackle more challenging problems,” Lian says.

The concept of fuel cells was first demonstrated in 1801, while the invention of the first working fuel cell occurred in 1842, when William Grove showed that an electrochemical reaction between hydrogen and oxygen could produce an electric current. NASA later developed fuel cell applications for the space program.

“Electrochemistry goes way back in science, and has many important applications, but our understanding of it remains largely empirical,” Lian says. “The Air Force wants to make a concerted effort to advance the field by boosting our understanding of electrochemical processes at the molecular and atomic level.”

The research team will develop software for electrochemical platforms as an experimental tool to gather data at the microscopic scale of processes such as the current-voltage curve generated in an electrochemical cell. The team will also develop theoretical tools to interpret the data. They will apply these experimental and theoretical tools to study fuel-cell technologies that use methanol and ethanol directly as fuels. These fuels are more energy dense than hydrogen, giving them the potential to greatly improve the range of fuel-cell vehicles, although their use in fuel-cell technology currently suffers from poorly understood side reactions that occur on electrode surfaces.

The software and theoretical tools that Lian’s team develops will be open source, allowing researchers in other labs to use it to simulate their own electrochemical experiments as well as interpret their data.

Providing these tools to the broader electrochemical industry will support widespread efforts for innovation and discovery, Lian says. “We hope to make a lasting impact in the field, opening doors to do things with electrochemistry that are currently out of reach.”

Over the past 30 years, DoD’s MURI program has brought significant new capabilities to U.S. military forces and opened up new lines of research. Notable examples include foundations in the fabrication of nanoscale and microscale structures by the processes of self-assembled materials and microcontact printing, the integration of vision algorithms with sensors to create low-power, low-latency, compact adaptive vision systems, and advances in fully optical data control and switching.

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Physics of a glacial 'slushy' reveal granular forces on a massive scale

The ridge in the right center of the photo shows where icebergs have broken off from Jakobshavn Glacier and tumbled into the water to form a slushy ice mélange — the world's largest granular material. Photo by Ryan Cassotto.

By Carol Clark

The laws for how granular materials flow apply even at the giant, geophysical scale of icebergs piling up in the ocean at the outlet of a glacier, scientists have shown.

The Proceedings of the National Academy of Sciences (PNAS) published the findings, describing the dynamics of the clog of icebergs — known as an ice mélange — in front of Greenland’s Jakobshavn Glacier. The fast-moving glacier is considered a bellwether for the effects of climate change.

“We’ve connected microscopic theories for the mechanics of granular flowing with the world’s largest granular material — a glacial ice mélange,” says Justin Burton, a physicist at Emory University and lead author of the paper. “Our results could help researchers who are trying to understand the future evolution of the Greenland and Antarctica ice sheets. We’ve showed that an ice mélange could potentially have a large and measurable effect on the production of large icebergs by a glacier.”

The National Science Foundation funded the research, which brought together physicists who study the fundamental mechanics of granular materials in laboratories and glaciologists who spend their summers exploring polar ice sheets.

“Glaciologists generally deal with slow, steady deformation of glacial ice, which behaves like thick molasses — a viscous material creeping towards the sea,” says co-author Jason Amundson, a glaciologist at the University of Alaska Southeast, Juneau. “Ice mélange, on the other hand, is fundamentally a granular material — essentially a giant slushy — that is governed by different physics. We wanted to understand the behavior of ice mélange and its effects on glaciers.”



For thousands of years, the massive glaciers of Earth’s polar regions have remained relatively stable, the ice locked into mountainous shapes that ebbed in warmer months but gained back their bulk in winter. In recent decades, however, warmer temperatures have started rapidly thawing these frozen giants. It’s becoming more common for sheets of ice — some one kilometer tall — to shift, crack and tumble into the sea, splitting from their mother glaciers in an explosive process known as calving.

Jakobshavn Glacier is advancing as fast as 50 meters per day until it reaches the ocean edge, a point known as the glacier terminus. About 35 billion tons of icebergs calve off of Jakobshavn Glacier each year, spilling out into Greenland’s Ilulissat fjord, a rocky channel that is about five kilometers wide. The calving process creates a tumbling mix of icebergs which are slowly pushed through the fjord by the motion of the glacier. The ice mélange can extend hundreds of meters deep into the water but on the surface it resembles a lumpy field of snow which inhibits, but cannot stop, the motion of the glacier.

“An ice mélange is kind of like purgatory for icebergs, because they’ve broken off into the water but they haven’t yet made it out to open ocean,” Burton says.

While scientists have long studied how ice forms, breaks and flows within a glacier, no one had quantified the granular flow of an ice mélange. It was an irresistible challenge to Burton. His lab creates experimental models of glacial processes to try to quantify their physical forces. It also uses microscopic particles as a model to understand the fundamental mechanics of granular, amorphous materials, and the boundary between a free-flowing state and a rigid, jammed-up one.

“Granular material is everywhere, from the powders that make up pharmaceuticals to the sand, dirt and rocks that shape our Earth,” Burton says. And yet, he adds, the properties of these amorphous materials are not as well understood as those of liquids or crystals.

In addition to Amundson, Burton’s co-authors on the PNAS paper include glaciologist Ryan Cassotto — formerly with the University of New Hampshire and now with the University of Colorado Boulder — and physicists Chin-Chang Kuo and Michael Dennin, from the University of California, Irvine.

The researchers characterized both the flow and mechanical stress of the Jacobshavn ice mélange using field measurements, satellite data, lab experiments and numerical modeling. The results quantitatively describe the flow of the ice mélange as it jams and unjams during its journey through the fjord.

The paper also showed how the ice mélange can act as a “granular ice shelf” in its jammed state, buttressing even the largest icebergs calved into the ocean.

“We’ve shown that glaciologists modeling the behavior of ice shelves with ice mélanges should factor in the forces of those mélanges,” Burton says. “We’ve provided them with the quantitative tools to do so.”

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DNA analysis adds twists to ancient story of a Native American group

"I want to help Native American tribes to reclaim knowledge of their very ancient evolutionary histories — histories that have been largely wiped away because of colonialism," says Emory geneticist John Lindo. Photo by Kay Hinton, Emory Photo/Video.

By Carol Clark

The ancient genomes of the Tsimshian indigenous people left tell-tale markers on the trail of their past, revealing that at least 6,000 years ago their population size was on a slow but steady decline.

The American Journal of Human Genetics published the findings, which draw from the first population-level nuclear DNA analysis of a Native American group from ancient to modern times.

“The finding contradicts a popular notion,” says John Lindo, a geneticist in Emory University’s Department of Anthropology and first author on the paper. “There is this idea that after Native Americans came in through the Bering Strait that they were all expanding in population size until Europeans showed up. At least for this one population, we’ve shown that was not the case.”

A boon in next-generation DNA sequencing technology has opened the possibility to explore the evolutionary history of different populations. “Ancient nuclear DNA analysis is a relatively new field,” Lindo says. “Not until recently have we had methods to sequence an entire genome quickly and inexpensively.”

Nuclear DNA provides information on an individual’s lineages going back hundreds of thousands of years. Lindo is one of the few geneticists looking at ancient whole genomes of Native Americans. He is especially interested in understanding how the genomes of their different populations evolved over time.

“Their evolutionary histories are radically different,” Lindo says. “Over thousands of years, various Native American populations have adapted to living in every ecology throughout North and South America, from the Arctic to the Amazon. That’s about as an extreme as you can get for differences in environments.”

The Tsimshian people historically lived in longhouses in coastal British Columbia and southern Alaska where they harvested the abundant sea life. Lindo and his colleagues sequenced the genomes of 25 living Tsimshian people and 25 ancient individuals who lived in the same region between 6,000 and 500 years ago, and confirmed that they were a continuous population through time.

Members of the Tsimshian Native American tribe hold a tea party near Fort Simpson, British Columbia, in 1889. Image from the Library and Archives Canada.

In a previous paper, drawing from the same data set, they found a dramatic shift between the two time periods in a class of genes associated with the immune system, suggesting a strong evolutionary pressure on the population to adapt to pathogens. A demographic model indicated a crash in the Tsimshian population size of about 57 percent during the early-to-mid 19th century. That finding fitted with historical accounts for how smallpox, introduced by European colonization, devastated the Tsimshian population during two epidemics within that time-frame.

The current paper looked at broader genetic variations between the ancient and modern DNA. An analysis showed both how the variation declined slowly in the ancient population before the collapse, but has since recovered.

“After a population collapse, only a subset of the genetic diversity remains,” Lindo says. “We find a more nuanced story, that despite the population collapse, the genetic diversity of modern Tsimshian people varies significantly.”

Intermarriage with other Native American groups and non-native populations increased the genetic diversity of some of the modern-day Tsimshian people so that it is near the levels prior to their population collapse, the analysis showed.

“A population with relatively high genetic diversity has a greater potential to fight off pathogens and avoid recessive traits,” Lindo says. “It exemplifies the benefits of gene flow between populations, especially following catastrophic events such as the small pox epidemics that the Tsimshian endured.”

Senior authors on the paper are Michael DeGiorgio from Pennsylvania State University and Ripan Malhi from the University of Illinois. The paper’s coauthors include Tsimshian representatives Joycelynn Mitchell and Barbara Petzelt from the Metlakatla Treaty Office in Prince Rupert, Canada.

Malhi, a leader in forging trusting relationships between genetic researchers and indigenous people, was a mentor to Lindo, who earned his PhD at the University of Illinois at Champaign-Urbana.

Lindo is continuing that tradition of building trust and working closely with indigenous populations. His ancient DNA research at Emory integrates the approaches of ancient whole genomes, statistical modeling and functional methods.

One of his projects is focused on genetic fluctuations to help understand ancient adaptions in various Native American populations. He is currently working with 10 different tribes from throughout North America.

“Community engagement is essential when working with indigenous communities,” says Lindo, explaining that he first meets personally with a tribal community to talk about how a genetic study might add to their knowledge of their own history.

“I listen to their stories and how they are working to keep their cultures alive,” he says. “One elder from a southwestern tribe told me that his grandfather was taken away in the early 1900s because he was a shaman and Christianity was swelling through the area. Each tribe’s stories are different but they are all powerful, and sometimes difficult, stories to hear.”

Most ancient DNA analyses have come out of Europe, where more ancient DNA labs are based and cold temperatures have helped preserve specimens.

Lindo wants to bring some of the same insights that those of European ancestry are gaining about their past to Native Americans.

“I’d like to disentangle this idea that Native Americans are part of a singular race,” he says. “I want to help Native American tribes to reclaim knowledge of their very ancient evolutionary histories — histories that have been largely wiped away because of colonialism.”

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Malawi yields oldest-known DNA from Africa