Finding Order in Insect and Orc Swarms

Ouellette's model of insect swarming

Ouellette’s model of insect swarming

By Olivia Zhu

Dr. Nicholas Ouellette looks for the organization in disorder.

Ouellette, associate professor in the mechanical engineering department at Yale University, studies collective motion in animal systems. On February 17, he presented his models of swarming of Chironomus riparius, the non-biting midge, as part of Duke’s Physics Colloquium. Ouellette ultimately hopes to pin down fundamental laws of biology through his physics research.

In the lab, Ouellette has found that Chironomus insects swarm in a columnar, teardrop shape in the center of their container. They only live in their flying state for two to three days, during which they mate, lay eggs and die. During this period, swarming affords them protection from predators and the opportunity to mate.

Ouellette and his lab have devised various methods of modeling the insects’ swarming. They found that the insect density remains constant, and that the “scattering,” or collisions of insects, mirrors that of an ideal gas over long periods of time. Interestingly, the graph of individual insect speed follows a Maxwell-Boltzmann distribution, even though the lab did not track the usual factors that create such a distribution, like temperature.

The most pressing question Ouellette would like to answer is which factors create a swarm—he has determined that close insect-insect repulsion contributes to swarming, but distant insect-insect attraction does not. To pursue this question, Ouellette is testing how many insects it takes to make a swarm.

Wildebeest stampede modeled in The Lion King

Wildebeest stampede modeled in The Lion King

Other animals that exhibit collective motion are mackerel, wildebeests and starlings. Some familiar examples of collective motion modeling are visible as the Orcs storm the castle in Lord of the Rings and as the wildebeests charge the canyon in The Lion King.

Why Meteorites Are So Hard to Find in North Carolina

by Erin Weeks

Note: This is the first in a multi-part series following Nick Gessler’s course on meteorites and the history of the solar system. Astronomy enthusiasts should check out the North Carolina Museum of History’s Astronomy Days happening this weekend, Saturday, January 25.

Visitors to Nick Gessler's lab can touch the moon -- literally -- and a whole lot of meteorites (Photo: Eric Ferreri)

Visitors to Nick Gessler’s lab can touch the moon — literally — and a whole lot of meteorites (Photo: Eric Ferreri)

A meteorite hasn’t been discovered in North Carolina in over 80 years, but Professor Nick Gessler dreams that his students will be the first to break that streak.

On the first day of his class at Duke, Gessler hauled in three tables worth of meteorites, chunks of rock and metal that hurdled through outer space for millions, even billions of years before surviving the descent into Earth’s atmosphere. Among his collection are pieces broken off from the moon, Mars and the dramatic Chelyabinsk meteorite that lit up Russia and YouTube in February 2013.

“That’s what they look like,” Gessler said, gesturing toward one table. “They’re ugly rocks.”

That’s not entirely fair. Past their melted, black crusts, most of the meteorites glint with flecks of iron. Some thin slices, when finely polished and held up to a light source, resemble stained glass. But ugly or no, the rocks have captivated human interest since people first observed them falling from the sky. Now, they’ve attracted Duke students in wide-ranging fields, from English and history to mathematics and engineering, united by a common interest in the extraterrestrial.

Gessler has a couple of theories about why North Carolina has seen a dearth of meteorite discoveries. First, farming practices have changed — farmers found many meteorites while tilling their land and dislodging the stony debris. These days, farmers rely on heavy machinery unfazed by rocks.

Second, Gessler thinks it’s possible that, despite our astronomical advances, light pollution may have clouded our chances of seeing minor meteors falling to earth.

“Maybe people just don’t look up at the sky like they used to,” he said.

Throughout this course, it seems certain his students will be looking up. Each has been assigned a North Carolina meteorite to research — they’ll ferret out old newspaper clippings and find when and where it fell, whether the land is private and what the likelihood of finding remnants now might be. Gessler will instruct them on the art and science of meteorite hunting, and eventually the students may put their skills to work in the field.

And who knows — some of them might even find the meteorites beautiful.

Supernova Explosion in M82: Exciting, but No Neutrinos

The M82 galaxy before (top) and after (bottom) its new supernova on Jan. 22 (Photo: UCL/University of London Observatory/Steve Fossey/Ben Cooke/Guy Pollack/Matthew Wilde/Thomas Wright)

The M82 galaxy before (top) and after (bottom) its new supernova on Jan. 22 (Photo: UCL/University of London Observatory/Steve Fossey/Ben Cooke/Guy Pollack/Matthew Wilde/Thomas Wright)

 

By Erin Weeks

In the early morning hours of January 22, the Earth turned spectator to a celestial event the likes of which hadn’t been seen in nearly three decades. The explosive death of a white dwarf star in Messier 82 (M82), a nearby galaxy, quickly ignited the astronomy world.

The supernova is exciting for a number of reasons that other outlets have well outlined — but unfortunately for Kate Scholberg, neutrinos are not one of them. Scholberg, a Duke University physics professor, studies the mysterious, nearly-massless particles at Super-K, a detector located deep in the mountains of Japan. Super-K was designed to spot neutrinos as they speed through Earth, revealing information about their sources, which can include the sun, cosmic rays, and supernovae.

“M82 is too far away for us to see any neutrinos from it,” Scholberg wrote in an email. “It’s about 11.4 million light years from us, meaning that the chance of seeing even a single neutrino from a core-collapse supernova in current detectors is probably a few percent or less (of course, we’ll look).”

Even if it were close enough, she said, this supernova doesn’t appear to be the type that generates a lot of neutrinos. White dwarves are common, dense stars whose supernovae are triggered when they consume new matter and experience runaway nuclear reactions. It takes a far more massive star to undergo core collapse, when a star’s unstable center caves in under the its own gravity.

“Core-collapse supernovae are the ones that spew neutrinos,” she wrote. “So, not much hope we’ll see anything in neutrinos, alas.”

Scholberg coordinates SNEWS, the SuperNova Early Warning System, which will sound the alarm at the first sign of a neutrino-generating supernova. SNEWS and Scholberg will have to keep waiting for the next big blast, but the white dwarf supernova in M82 is still great news for physicists who study another hot topic — dark energy.

Astronomers spotted the supernova unusually early, meaning they’ll be able to collect a wealth of data before it hits peak brightness in a couple of weeks. It may be possible then to see the supernova with just a set of binoculars.

A six-photo composite of the starburst galaxy M82 (Photo: NASA, ESA, and The Hubble Heritage Team [STScI/AURA])

A six-photo composite of the starburst galaxy M82 (Photo: NASA, ESA, and The Hubble Heritage Team [STScI/AURA])

Detecting Dark Matter: the LUX experiment

Photomultipliers of the LUX detector

Photomultipliers of the LUX detector

By Olivia Zhu

How far would people go to detect something that, by definition, isn’t there?

Scientists from the Large Underground Xenon (LUX) experiment have built a facility a mile underneath the black hills of South Dakota in hopes of finding evidence of dark matter. Dark matter currently “does not exist” because it cannot be detected with light; however, it must be there, as it exerts a gravitational force on “normal” matter. Actually, it should have a rather large presence: the universe is made of 4.9% normal matter, 26.8% dark matter, and 68.3% dark energy.

On Jan. 16, Carmen Carmona-Benitez, a LUX representative from Case Western Reserve University in Cleveland, presented LUX’s latest findings to Duke’s Physics Department. The LUX experiment hopes to detect the presence of weakly interacting massive particles (WIMPs), a candidate component of dark matter. Carmona-Benitez described their detector, which has photomultipliers at either end; these photomultipliers will sense light emitted from electrons when WIMPs collide with their nuclei.

The LUX experiment, comprising 100 people, is a collaboration of 17 institutions in the United States and a few internationally. How could 100 extremely talented scientists work together without butting heads? Well, Carmona-Benitez stressed that many of the scientists design the machinery supporting the primary WIMP detector. For example, the team at University of California Santa Barbara built a filter system for the enormous tank of water that shields the detector from external gamma radiation. Another team contributed four thermosyphons used to cool the detector.

Thanks to these various efforts, LUX has achieved unprecedented sensitivity to WIMPs; however, no WIMP has been detected. This suggests that WIMPs, in fact, do not exist, and therefore do not comprise dark matter. The LUX team, though, refuses to give up and is creating a new and improved LZ experiment for WIMP detection.

The Triangle Universities Nuclear Laboratory (TUNL), based at Duke, is also trying to understand dark matter by studying neutrinos.

New Blogger: Olivia Zhu

196034_10150927127403780_429300165_n-2Hi!  My name is Olivia Zhu, and I am a sophomore biophysics major hailing from Pleasanton, California. I’m thrilled to start writing for the Duke Research Blog.

When I started my Duke career, I had absolutely no idea what research was. I had a vague conception of it as a drawn-out, painstaking process in which one traded in his life’s freedom for a micropipette. However, midway through my freshman year, a conversation with Professor Henry Greenside prompted me to reconsider. Professor Greenside inverted my perspective on research: he showed me that research did not revolve around tedious procedures, but rather around the pursuit of answers to fascinating questions. Since then, all sorts of research topics, particularly those with some aspect of physics, have captivated me. I found that research fulfills the idealistic conception I have always held of education: research represents the ultimate pursuit of pure knowledge, often without the pressures of immediate practical application.

Currently, I work in the Mooney Lab of neurobiology, which studies the learning processes in songbirds. Via surgical viral infection, I am examining the role that dopamine plays in this circuit.

In other matters, I enjoy forsaking my science-based identity by taking English, art, and history classes. I play soccer, run around campus, read classic novels, and discuss philosophy with friends. At Duke, I am a part of the Round Table and pWILD communities. Sometimes I miss hiking in California or exploring the islands in Beaufort, North Carolina, but I know there’s no place I’d rather be than here in Durham.

I’m looking forward to sharing my exploration of research at Duke!

Keely Glass, the Omni-Chemist

Guest post by Addie Jackson, North Carolina School of Science and Mathematics

Keely's picture from Linked-In

Keely’s picture from Linked-In

Ask Keely Glass how she would describe her research to a third grader, and she laughs while thinking of the best way to explain.

“So, say you’re sitting next to your friends. One has really black hair and one has red hair. They have different hair colors, because their hair colors come from the different pigments. Your friend with black hair has more eumelanin, while your friend with red hair has pheomelanin.”

A PhD candidate in the chemistry department at Duke, Glass currently does research on analytical methods to analyze these pigments in biological and historical samples. She’s also using those skills to provide direct chemical evidence for the presence and preservation of eumelanin in the fossil record.

Trust us, that's a fossil squid. (Courtesy of Willsquish on Wikimedia Commons.)

Trust us, that’s a fossil squid. (Courtesy of Willsquish on Wikimedia Commons.)

Glass elaborates by describing a common fascination with squids, also known as cephalopods, who release pure black eumelanin when faced with a predator. Two kinds of melanin are present in nature: eumelanin (brown to black in color) and pheomelanin (yellow to red). Through her work, she and her team have verified that eumelanin is preserved in the fossil record, and showed that it can be identified directly using its known chemical signature. They have also found that the eumelanin identified in the fossil record is not significantly different from the modern eumelanin, meaning it hasn’t evolved in the more than 160 million years since.

Another lab at Duke, run by Professor Warren S. Warren, uses a pump-probe microscopy system to characterize melanins to attempt to find statistically significant variations between melanomas (skin cancers) that do not develop metastases. The hope for this project is to improve diagnostic accuracy for these metastatic melanomas, through analyzing the melanin distribution in “old” archived (stored for >10 years) tissue samples. Glass says, “The paper I wrote with them essentially says if melanin resists degradation (stays intact and doesn’t alter) over more than 160 million years, it’s fairly clear that it will resist degradation in storage for 10 years. In other words, it’s pretty clear that these archived tissue samples are still viable for melanin analysis.”

Fourteen months in the life of one man's nodular melanoma. (Courtesy of 0x6adb015 via Wikimedia commons.)

Fourteen months in the life of one man’s nodular melanoma. (Courtesy of 0x6adb015 via Wikimedia Commons.)

Working with the Warren group, Glass also found that the pump-probe system was sensitive to the higher iron-concentration fossilized squid melanin as compared with modern cephalopod melanin. They were able to mirror the iron-independent signal by adding iron to modern cephalopod melanin. This proved to be interesting because metastatic melanomas have increased iron levels, which may or may not be responsible for signature variations.

The classical fields of chemistry (analytical, organic, physical, theoretical, inorganic, and biological) have become more integrated over time, making the labels themselves increasingly obsolete. To better label themselves, most chemists mix and match:  “I’ve called myself at various times a ‘Bioanalytical Chemist,’ ‘Biophysical Organic Chemist,’ ‘Analytical Biochemist,’ ‘Organic Geochemist’ etc. to emphasize that the systems I’ve worked on, the techniques I’ve used, and the skills I’ve obtained are diverse and dependent on the project I’m defining.”

Glass says, “When I think that the names have gone a little haywire, I jokingly call myself an omni-chemist. Like most chemists I work on diverse array of projects that require techniques and knowledge from many fields.”

Addie Jackson interviewed Keely Glass and wrote this post as part of a Science Communication seminar led by NCSSM Dean of Science Amy Sheck.