Volume 2, Issue 15 October 2005
Insect Flight, Sans Wings
Next month, UC Berkeley integrative biologist Robert Dudley will travel deep into the rainforests of Panama. What will he and his research team do during this field study? "Mostly we'll be tossing ants," he says. Dudley isn't joking. He's a leading expert in animal flight — bees, birds, hummingbirds, and even ants that manage incredibly sophisticated airborne maneuvers without wings.
Robert Dudley also conducts research on Southeast Asian flying lizards and the flight performance of hummingbirds and bumblebees at various elevations.
"I'm interested in the biodynamics of flight, including aerodynamics, physiology, form, structure, and evolution," Dudley says. "There are a lot of things up in the air, so the motto of our lab is essentially 'all taxa, all the time.'"
Dudley's trip this fall is the next step in a groundbreaking exploration of how wingless flight has evolved throughout myriad species in the animal world. The project began last year when insect ecologist Stephen P. Yanoiviak of the University of Texas Medical Branch was high in the forest canopy outside Iquitos, Peru, studying mosquitoes. Brushing some annoying ants off his arm, he noticed that they managed to land back on the tree trunk below. It turned out that the ants were capable of directed descent — they literally glided to their target.
Shortly after his initial observation, Yanoiviak called in Dudley and University of Oklahoma ant ecologist Michael Kaspari to study the surprisingly excellent pilots.
The Darth Vader of the ant world, Cephalotes atratus, lives in the tropical forest canopy of South and Central America. Almost a centimeter long, its long hind legs and flanged head shield may be the key to its newly discovered ability to glide back to its home tree after falling or dropping. (photo by Steve Yanoviak)
"The ants glide backwards but we don't understand the mechanisms," Dudley says. "They start tumbling and then swoosh... they land right where they want to be."
Meeting in Panama where the same species of ants are found, the three researchers captured high-speed video of the bugs falling. The special camera enabled them to slow down the footage to dissect the ants' subtle and fast motions. Apparently, the insects use their legs as flaps.
"As the ant falls away from the tree trunk, the left hind leg goes toward to the left to increase the drag and provide rotation as it comes in for landing," Dudley says. "The amazing thing is that you can cut off the hind legs and it'll still land on the target trunk. The arthropods have incredible structural redundancy."
To identify the minimal structures required for gliding, the researchers are surgically removing body parts and observing how flight is affected. In one such ablation experiment, they left the legs intact but removed the abdomen. Even with 30 percent of their bodyweight gone, the ants still managed to hit their targets, Dudley says. Just don't blind them.
Recently, Dudley and Yanoviak determined that the ants rely on the reflectance and color of the tree trunk to orient their trajectories as they fall. By hanging strips of colored cloth and "tossing the ants," as Dudley phrases it, they determined that the ants direct their descent toward lighter colors.
The researchers hung fabric strips in the forest as surrogate tree trunks to examine how color affects directed aerial descent behavior. (photo courtesy the researchers)
"In the forest, tree trunks are covered with lichen crusts that look white against the vegetation," Dudley says. "So the high contrast certainly provides a good visual target for the falling ants."
The researchers recently received a National Geographic Society grant to continue the gliding ant research in Amazonian Peru and Panama. By collecting more high-speed video, Dudley hopes to better understand the gliding mechanism. For example, even though the ants fall at nearly 4 meters per second at a steep angle and sometimes bounce off the trunk, they're capable of quickly turning around mid-air and trying again. These kinds of aerodynamic tricks are most likely achieved through precisely orchestrated movements of the legs, abdomen, and head.
While ant gliding has much to tell us about morphology and flight, the airborne ants will probably not provide much insight into the evolution of flying insects. That's because ants once had wings and lost them to history, Dudley explains. A more primitive taxon that never had wings but still exhibit directed descent, such as silverfish, would be more likely to reveal the evolutionary connection between gliding and winged flight, Dudley says.
The ant C. atratus is only one of many ant species found to glide when dropped from a branch high in the forest canopy. They may have developed this ability to avoid almost certain death if they were to land on the forest floor or in water that floods the Amazonian forest much of the year. These ants were photographed near Iquitos, Peru. (photo by Steve Yanoviak)
"Flight may have started out as a way of controlling landing which otherwise could be pretty bad if an insect falls," Dudley says. "And so gliding might be a pre-existing behavioral substrate for subsequent elaboration into morphological structures that could perhaps turn into wings."
The beauty is that silverfish can be easily reared in the laboratory. All of the necessary experiments, from ablation to high-speed video, could be conducted right on the Berkeley campus instead of far away in the field, he says. Time will tell if silverfish, a pest to most of us, might just hold the secret history of insect aerodynamics.
"The origins of flight are murky," Dudley says. "The fossil record is either not good or totally absent in this regard. But studying directed descent could give us a stunning experimental avenue into the evolution of insect flight."
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Astrophysics Via Helium Balloon
On June 1, UC Berkeley astrophysicist Steve Boggs and a team of graduate students and postdocs gazed into the sky as three years of research vanished into thin air. They were watching a prototype telescope they built ascend into the atmosphere on its maiden voyage. It took a long time before the craft carrying their instrument was out of sight. That's because the telescope wasn't stowed inside a rocket, but rather hanging in the canopy of a massive unmanned helium balloon slowly ascending to the edge of space.
Steven Boggs polishes a thermal shield for the Nuclear Compton Telescope.
"Launching a small satellite carrying a telescope into orbit costs around $100 million," says Boggs, an assistant professor in the Department of Physics. "But for about $1 million, a balloon can get you above 99 percent of the atmosphere. So balloon flights are great for testing out new instruments that may eventually go up in space."
The telescope was built at UC Berkeley's Space Sciences Laboratory where Boggs specializes in gamma ray astronomy. The rays are of such high energy that they can travel incredibly long distances to give us glimpses of phenomena in the deepest regions of space.
"Gamma ray astrophysics is the study of some of the most exotic things our universe has to offer, like matter falling into the edge of a black hole or the surface of neutron stars," Boggs says.
For example, late last year the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI), a satellite launched by UC Berkeley and NASA in 2002, captured the brightest gamma ray explosion ever observed. The giant gamma ray that burst from the other side of our galaxy was powerful enough to affect the Earth's atmosphere.
The Nuclear Compton Telescope hangs from a crane awaiting attachment to the balloon at the Fort Sumner launch site.
"Gamma ray bursts are explosions that, in a fraction of a second emit, almost the entire energy of the sun in gamma rays," says Boggs, a collaborator on the RHESSI project.
The telescopes that Boggs and his team build and use are odd in that they have no optics. That's because the gamma rays are so high energy that they pass right through the lenses or mirrors of traditional telescopes.
As a result, gamma ray telescopes must gather data more indirectly. The prototype Nuclear Compton Telescope that flew aboard the balloon employs a physics principle called Compton Scattering. The instrument's detectors calculate the arrival direction and energy of the incoming gamma photons. This particular telescope is designed, Boggs says, to "witness the fires of creation."
The NASA balloon is inflated in preparation for launch.
In the earliest moments of the universe, the Big Bang produced helium, hydrogen, and small amounts of other elements. The rest of what surrounds us was created in the meantime, Boggs explains. One of the best ways to understand how these elements are produced is to examine their radioactive decay, he says. Frequently, the instability of an element's nucleus causes it to decay, resulting in another element. The Nuclear Compton Telescope seeks out particular gamma rays that correspond to specific radioactive decays.
"That way, we know that these atoms were just created on the scale of hundreds to millions of years ago," Boggs says. "By studying them, we can better understand how elements are forming today."
Even on its first balloon trip, the Nuclear Compton Telescope likely gathered valuable scientific data. Launched in collaboration with NASA, the balloon the size of a football field carried the telescope in a canopy about as bulky as a small truck. The instrument itself is the size of a shoebox but the support electronics filled the canopy to capacity. After departing at sunrise from Fort Sumner in eastern New Mexico, the balloon spent the entire afternoon at altitudes of 35 to 40 kilometers. It finally touched down at sunset in southwestern New Mexico right in the middle of an outdoor art installation called the Lightning Field.
NASA illustration from 2003 depicting the RHESSI satellite capturing a gamma-ray burst flashing just off the limb of the sun, measuring for the first time the polarization of these gamma rays.
The flight was a success, Boggs says, save for a few dents suffered on landing. In the months since, they've begun to analyze the scientific data collected during the flight while simultaneously preparing the instrument for a two or three week flight in 2007, when they'll launch from Australia and hopefully fly the instrument around the world.
"You really have to be in the southern hemisphere to see the bulk of our galaxy," Boggs says.
While this prototype contained just two gamma ray detectors, the next generation will carry twelve. Once the advanced model proves itself, Boggs hopes to work with NASA or a foreign collaborator to launch the instrument into orbit on a satellite.
"These instruments enable us to study matter in very extreme environments that are far more exotic than what we can create in laboratories on Earth," Boggs says.
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Catalyzing Nanotechnology
As scientists and engineers continue to make progress in the realm of nanotechnology, new tools become necessary to synthesize more complicated structures on such tiny scales. UC Berkeley chemical engineer Alexander Katz is developing several techniques to fashion structures that spur specific chemical reactions but are as small as a single nanometer. His processes range from a cookie-cutter templating technique to methods directly inspired by Mother Nature. Eventually, the materials that Katz and his collaborators discover could speed the development of nanoscale electronic components for future computers and related memory systems.
Alexander Katz and his colleagues have a U.S. patent on one of their methods to bind functional groups on surfaces discovered at Berkeley, with two others currently pending.
"Standard lithographic etching used to make microprocessors is certainly able to create mechanical features of the right size and shape," Katz explains. "But as these features become smaller in the future, what becomes as important as their size and shape is local arrangement of chemical functional groups. How can we organize these groups and the environment surrounding them in solids?"
Because of their small size, the structures that Katz's research group synthesizes can be used as active catalytic sites for causing chemical transformations to occur. Chemists use catalysts to speed the rate of chemical reactions. The catalyst acts as a pathway between the reactants and the end product that requires less of an energetic barrier than the transformation would take otherwise. Because the nanoscale order in Katz's sites can interact with a reactant molecule specifically, these sites can induce chemical reactions with great selectivity. For instance, some of Katz's sites can steer the product of a chemical reaction to be one or another molecule, depending on the functional group arrangement. The most proficient examples of how elaborate organization of functional groups can affect catalysis can be found inside of each of us.
After immobilizing gold nanoparticle imprints in silica, the gold core is etched to expose the chemical functional group organization on the gold surface that is tethered off of the silica network. The three images depict the shrinking core of colloidal gold (black) over a period of 22 hours. (courtesy the researchers)
"The functional groups that keep us alive consist of relatively simple building blocks," Katz says. "But the way they're assembled is intricate. It's that assembly that imparts elaborate catalytic properties."
Molecular imprinting in silica is a method Katz and his colleagues developed to achieve nanoscale functional group organization in solids. The researchers take a particular molecule and mold silica around it. The molecule is then removed but chemical functional groups are left attached to the inside of the mold. The end result is a solid, visually not unlike an ordinary piece of glass, but actually riddled with miniscule imprinted pores. Organic molecules bind inside these pores where the imprinted functional groups promote a chemical reaction.
The researchers have also explored a method to imprint bulk silica with particle templates as large as 15 nanometers. Rather than organize several functional groups at a time, the synthesis of nanoparticle building blocks for bulk silica imprinting is ideal for organizing thousands of functional groups at once, Katz says.
This slide depicts the synthetic and biological catalysts consisting of similar organic and organometallic active sites. The confined environment surrounding both biological catalysts results from the hydrophobic interior of the enzyme. The researchers successfully replicated this confinement in the synthetic equivalents of the biological active sites shown on the right side of this figure. (courtesy the researchers)
The process is similar to the single-molecule imprinting, but in this case a nanoparticle with a functional group organized on its surface is bound in the silica. After the nanoparticle core is removed, the organized functional groups remain immobilized in the structure.
In another technique that Katz and his coworkers discovered, bowl-shaped functional groups are grafted to the surface of a piece of silica. The functional groups act as one nanometer-sized "pocket" that only allows certain catalytic reactions to occur. The rim of the pocket and the surface of the silica can also be altered to affect the catalyst properties.
"The mechanism and the selectivity of these reactions, in addition to catalyst activity, can be dictated by our ability to organize chemical functional groups in solids," Katz explains. "All of our efforts are about taking something ordinary, like these functional groups, and enabling them to do extraordinary things when arranged cooperatively within a nanoscale site."
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Berkeley's Scientific Legacy
Luis Alvarez, adventurer physicist
Luis W. Alvarez was an adventurer physicist. The two terms may seem an odd combination until one considers Alvarez's career. A member of the National Inventor's Hall of Fame, Alvarez developed the proton linear accelerator, patented three types of radar still used today, designed an instrument that for 15 years served as the universal standard of length, co-discovered the hydrogen isotope tritium, searched for hidden chambers in an Egyptian pyramid, analyzed the Zapruder film documenting John F. Kennedy's assassination, and won the 1968 Nobel Prize in physics. And that's just the short list.
Luis W. Alvarez served on President Richard Nixon's Scientific Advisory Committee. (courtesy Berkeley Lab)
Alvarez was born June 13, 1911, in San Francisco. His father was Walter C. Alvarez, a famous physician/medical columnist.
"I had the good fortune as a boy to be exposed to the electrical and mechanical apparatus in my dad's laboratory," Alvarez once said. "He realized I would probably go into experimental science of some sort, so he apprenticed me for two summers to a scientific instrument-maker's machine shop."
His father's encouragement paid off. After switching from chemistry to physics, Alvarez earned his PhD at the University of Chicago. At the time, his sister was the secretary of famed UC Berkeley physicist Ernest O. Lawrence. The two met and in 1936 Lawrence offered Alvarez a research assistant job at the groundbreaking Radiation Laboratory that would eventually become Lawrence Berkeley National Laboratory.
Just before World War II began, Alvarez co-discovered tritium, a source of thermonuclear energy. During the war, he invented aviation and radar technology and was a member of the Manhattan Project that developed the atomic bomb. Indeed, Alvarez flew in the plane trailing the aircraft that dropped the atomic bombs on Hiroshima and Nagasaki. The physicist was onboard to observe the effects of the blast.
Luis Alvarez with his bubble chamber. (courtesy Berkeley Lab)
After the war ended, Alvarez returned to the University and designed a proton linear accelerator that was the basis of today's systems for creating high-energy radiation. Then, in 1953, he attended a meeting of the American Physical Society where his eventual Rad Lab colleague (and 1960 Nobel Laureate) Donald Glaser presented his bubble chamber, a device to study subatomic particles. Alvarez improved upon Glaser's instrument and used it to discover a large number of resonance states, subatomic particles that can't be directly detected because they live for so short a time. Glaser's use of his hydrogen bubble chamber and data analysis equipment enabled the researchers to deduce the existence of the resonance states. In 1968, he won the Nobel Prize in Physics "for his decisive contributions to elementary particle physics."
Over the following years, Alvarez would embark on a variety of projects. He analyzed the film of JFK's assassination to determine the number of shots fired. With a team of LBL researchers, he used cosmic rays to probe the Egyptian pyramid of Cephren for hidden chambers. In 1980, he and his son Walter Alvarez, a UC Berkeley geologist, first posited the now widely-accepted theory that a giant asteroid crashed into the Earth 65 million years ago, spewing smoke in the atmosphere that blocked the sun, eventually leading to the death of the dinosaurs.
Luis Alvarez's autobiography, Adventures Of A Physicist, was published in 1987. He died the following year.