Evan M. Lerner

Evolution in extreme environments has produced life forms with amazing abilities and traits. Beneath the waves, many creatures sport iridescent structures that rival what materials scientists can make in the laboratory.

A team of researchers from the University of Pennsylvania and the University of California, Santa Barbara, has now shown how giant clams use these structures to thrive, operating as exceedingly efficient, living greenhouses that grow symbiotic algae as a source of food.

This understanding could have implications for alternative energy research, paving the way for new types of solar panels or improved reactors for growing biofuel. 

The study was led by Alison Sweeney, assistant professor in the Department of Physics and Astronomy in Penn’s School of Arts & Sciences, and Daniel Morse, professor emeritus in UCSB’s Department of Molecular, Cellular and Developmental Biology and Director of its Marine Biotechnology Center. The team also includes lead author Amanda Holt, a postdoctoral researcher formerly at UCSB and now at Penn, as well as Sanaz Vahidinia of NASA’s Ames Research Center and Yakir Luc Gagnon of Duke University.

It was published in the Journal of the Royal Society Interface.

“Many mollusks, like squid, octopuses, snails and cuttlefish,” Sweeney said, “have iridescent structures, but almost all use them for camouflage or for signaling to mates. We knew giant clams weren’t doing either of those things, so we wanted to know what they were using them for.”

While the true purpose of these iridescent structures, cells known as iridocytes, was not known, the team had a strong hypothesis. Like neighboring coral, giant clams are home to symbiotic algae that grow within their flesh. These algae convert the abundant sunlight of the clams’ equatorial home into a source of nutrition but are not particularly efficient in the intense sunlight found on tropical reefs; sunlight at the latitude where these clams live is so intense that it can disrupt the algae’s photosynthesis, paradoxically reducing their ability to generate energy.

The team members began their study hypothesizing that the clams’ iridocytes were being used to maximize the usefulness of the light that reaches the algae within their bodies. They were first confounded by the relationship between these iridescent structures and the single-celled plants, until they realized that they had an incomplete picture of their geometry. When they made more precise cross sections of the clams, they found that the algae were organized into pillars, with a layer of iridocytes at the top.

“When we saw the complete picture, we understood that the pillars are oriented exactly the wrong way if you want to catch sunlight,” Sweeney said. “That’s where the iridocytes come into play.”    

The team relied on Amanda Holt and Sanaz Vahidinia to model exactly what was happening to the light once it passed through the iridocytes; the degree of disorder within these cells bore a resemblance to structures Vahidinia studies at NASA: the dust of Saturn’s rings.

Their analysis suggested that the iridocytes would scatter many wavelengths of light in a cone-like distribution pointing deeper into the clam. Red and blue wavelengths, the most useful to the algae, spread the widest, impacting the sides of the pillars in which the single-celled plants were stacked.

To test this model, the team constructed fiber optic probes with spherical tips the size of an individual alga. Threaded through a section of clam flesh alongside the native algae, this spherical probe was able to detect the angled light scattered by the iridocytes, whereas a flat-tipped probe, only able to sense light shining straight down, detected nothing.

“We see that, at any vertical position within the clam tissue, the light comes in at just about the highest rate at which these algae can make use of photons most efficiently,” Sweeney said. “The entire system is scaled so the algae absorb light exactly at the rate where they are happiest.”

“This provides a gentle, uniform illumination to the vertical pillars consisting of the millions of symbiotic algae that provide nutrients to their animal host by photosynthesis,” said Morse. “The combined effect of the deeper penetration of sunlight — reaching more algae that grow densely in the 3-dimensional volume of tissue — and the “step-down” reduction in light intensity — preventing the inhibition of photosynthesis from excessive irradiation — enables the host to support a much larger population of active algae producing food than possible without the reflective cells.”     

Mimicking the micron-scale structures within the clam’s iridocytes and algal pillars could lead to new approaches for boosting the efficiency of photovoltaic cells without having to precisely engineer structures on the nanoscale. Other alternative energy strategies might adopt lessons from the clams in a more direct way: current bioreactors are inefficient because they must constantly stir the algae to keep them exposed to light as they grow and take up more and more space. Adopting the geometry of the iridocytes and algal pillars within the clams would be a way of circumventing that issue.

“The clam has to make every square inch count when it comes to efficiency,” Sweeney said. “Likewise, all of our alternatives are very expensive when it comes to surface area, so it makes sense to try to solve that problem the way evolution has.”

The research was supported by the Army Research Office and the Office of Naval Research.

The University of Pennsylvania will officially open the region’s premier facility for advanced research, education, and innovative public/private partnerships in nanotechnology on October 4. The 78,000 square-foot Krishna P. Singh Center for Nanotechnology will serve as the University’s focal point for groundbreaking work in the emerging field of nanotechnology, which involves the manipulation of matter on an atomic and molecular scale.

The potential benefits of nanotechnology range from regenerative medicine and targeted drug delivery systems, to innovative new approaches in creating and storing electricity that could virtually eliminate the use of fossil fuels, to highly efficient ways of harvesting fresh water from seawater, to everyday commercial products that make clothes last longer, golf balls fly straighter and personal computers operate more efficiently.

“The Singh Center positions Penn to become our nation's leader in nano-scale science, education and research," said Penn President Amy Gutmann. “This is a stunning building that will bring together eminent Penn researchers and experts in private industry with state-of-the-art laboratories and production facilities. Nanotechnology is a vital field with tremendous momentum and vast opportunities for innovation and positive impact locally, nationally and globally. The Singh Center is a critically important part of Penn’s mission to advance both basic discovery and the application of those discoveries to improve society.”

Faculty from the School of Engineering and Applied Science, the School of Arts and Sciences, and across the University will make use of the Singh Center’s characterization and fabrication suites. Each of the two 10,000-square-foot facilities is filled with state-of-the-art equipment and designed to enable the high-precision techniques that research at the smallest scales necessitates.

The characterization facility is situated on bedrock, 18 feet below the surface, to help minimize vibrations that would interfere with its various atomic and electron microscopes. Its labs are also designed to be isolated from temperature fluctuations, atmospheric turbulence, and electromagnetic noise.

The fabrication facility on the Singh Center’s ground floor contains a next-generation cleanroom. Once in isolation garb, researchers will use its assembly tools to grow carbon nanotubes, deposit graphene, and etch microelectronic systems, among many other applications. The facility’s photolithography equipment is shielded from interfering ultraviolet light by a pane of marigold glass, which gives the Center its signature color.

“Penn’s world-class researchers need world-class facilities to advance their groundbreaking work,” said Eduardo Glandt, the Nemirovsky Family Dean of the School of Engineering and Applied Science. “Likewise, the Singh Center will play a key role in growing our faculty and research expertise for years to come.”

Beyond serving faculty in engineering, physics, and chemistry, the Singh Center was built to spark interdisciplinary inquiry. An inviting gateway at the eastern entrance to campus, the Center is already opening doors to new research throughout Penn’s 12 schools.

“The Singh Center’s facilities will allow researchers from a range of fields to analyze structure in the finest possible detail, from anthropologists working with ancient artifacts to biomedical researchers developing therapeutic molecules,” said Steven Fluharty, dean of the School of Arts and Sciences. “Its impact will be felt far beyond the field of nanotechnology.”

The Singh Center will also help Penn-developed technology move from the lab to the marketplace via connections with local industry development leaders such as the Nanotechnology Institute and Ben Franklin Technology Partners, as well as Penn’s internal commercialization engine, the Center for Technology Transfer. Existing industry members, from pharmaceutical companies to computer chip designers, will also make use of the Singh Center’s characterization and fabrication facilities.

“The Singh Center is one of the few places in the world where you can find this kind of equipment and expertise in the heart of a major metropolitan city,” said Mark Allen, the Singh Center’s scientific director. "In addition to enabling world-class research and providing outstanding educational opportunities in nanotechnology, we aim to be a two-way street for entrepreneurship and innovation.”

The building was designed by Weiss/Manfredi Architecture/Landscape/Urbanism, a multidisciplinary design practice based in New York City. Founded by Marion Weiss and Michael Manfredi, Weiss is the Graham Chair Professor of Architecture in Penn’s School of Design. The team’s challenge was to create a building that evoked the mathematical precision of nanotechnology while being integrated into the large scale of Penn’s urban campus. The results have been met with resounding praise from the architecture world: The Singh Center has already won a 2013 American Architecture Award and a 2013 International Architecture Award, presented by the Chicago Athenaeum Museum of Architecture and Design and the European Centre for Architecture Art Design and Urban Studies.

The Singh Center was made possible by a $20 million gift by Krishna P. Singh. Singh is the founder, president and chief executive officer of Holtec International in Marlton, N.J., an energy-technology company he established in 1986. He is a member of Penn's Board of Trustees and the Engineering Board of Overseers and has served as an adjunct professor of mechanical engineering at Penn. He received his Ph.D. in mechanical engineering in 1972 from Penn and a master's in engineering mechanics in 1969, also from Penn.

On Friday, Sept. 4, nearly 2,000 of the world’s top young computer scientists and engineers assembled in the bowl of the Wells Fargo Center. They were awaiting the start of PennApps, the world’s largest collegiate hackathon.

In the opening ceremony, Vijay Kumar, the Nemirovsky Family Dean of the School of Engineering and Applied Science, put a fine point on the purpose of the event.

“Hacking is the noblest form of research,” Kumar said.

Though it conjures images of cybercrime, for engineers, “hacking” is the embodiment of the ingenuity it takes to solve a problem. Over the next 36 hours, PennApps contestants vied against one another to make the best possible pieces of software and hardware—and were also teaching and learning from their peers.

While the crucible of a competition featuring more than $60,000 in prizes is a motivator, students, including hundreds of high-schoolers, come to PennApps to push the boundaries of what they can do with computers.

“Whether you win the grand prize or just make your first working program and put it on the App Store, both of those are equally gratifying,” says Pranav Vishnu Ramabhadran, PennApps’ director.

Ramabhadran, a senior in the Jerome Fisher Program in Management and Technology, a dual degree program with the Engineering and Wharton schools, is carrying the torch for PennApps, an organization founded in 2009. The student group has hosted 11 such competitions in the past.

The hackathon has evolved significantly since it launched with just 17 teams, which were all from Penn. This year’s program, PennApps XII, featured hundreds of groups, hailing from around the nation, India, Denmark, Singapore, Australia, and more.

The weekend’s proceedings—from teams’ travel costs, to catering, to the space itself—were entirely made possible though sponsorships arranged by the students behind PennApps. Foremost among these sponsors was Comcast, the owner of the Wells Fargo Center, which was eager to show its arena’s new technical capabilities and scout rising talent.

As part of their recruiting efforts, other sponsors were happy to lend or donate their hardware as testing platforms, and PennApps provided a parts library, plus soldiering and 3D-printing stations, to help contestants build their own. Still, many contestants’ suitcases were stuffed, not with clothes, but the chips and wires necessary to realize their ideas.

Sponsors also incentivized participants with a series of prize categories for using their technology. Apple watches, Microsoft tablets, and more fungible rewards, like bitcoins or gift cards, were in play.

New this year was the inclusion of routes, or thematic categories contestants could enter their projects into. The top “Health” hack was a program that could help detect skin cancer by taking a picture of a mole, while the top “Civic” hack provided an easier way of filling out various government forms. Runners-up for the best overall hack included a tool for measuring a person’s gait and a search engine designed for codebases.

The grand prize winning team, Fifth Sense, developed an assistive device that connects to smartphones and allows input and output in braille. Carnegie Mellon sophomores Edward Ahn, Cyrus Tabrizi, Rajat Mehndiratta, and Vasu Agrawal also took home prizes in two other categories, including best “Hardware” hack.

It was this combination of ingenuity and problem solving that impressed the panel of judges—made up of representatives from local tech and venture capital firms—and is sending the team on to an invite-only hackathon at Facebook headquarters.

It also embodies the envelope-pushing spirit of PennApps.

“Hacking is really taking the best of what you have around you and making something new,” says PennApp’s Ramabhadran. “It’s taking the normal stuff and doing something unconventional with it.”

EVERYONE KNOWS professional wrestling is scripted. What most people don’t know is that there's really only one script. Found in virtually every form of literature for centuries, it draws upon the most basic story structure in existence and is told in three acts.

ACT 1: The good guy (or face) squares off against the bad guy (or heel) until the heel gets bored with the rules and uses dirty tactics to gain the upper hand.

ACT 2: The heel then shows off his nefarious abilities, beating our hero within inches of defeat.

ACT 3: The face shoots his shoulder out of a pin just as the ref’s hand is coming down for the final count, shows off all of his really fancy moves and finally vanquishes the heel.

OK, SO MAYBE the part about launching a shoulder out of a pin before the three-count hasn't been around for centuries, but you get the idea. There are many variations of the above, but the same basic structure has been playing out in big arenas, bingo halls, and barns for more than a century since pro wrestling’s birth as a carnival sideshow, where onlookers were bilked out of their money by a hero’s improbable victory.

And no one does this like Hulk Hogan.

Hogan has been wrestling since 1977 and has been the world’s most famous wrestler for most of the time since. His ascendency within the World Wrestling Federation (now the WWE) made him the personification of the industry, an ’80s icon, and an avatar for a nation unnerved by the Soviet Union's arms buildup, Iran's hostage-taking habit, and Japanese economic encroachment. There was no mystery that Hogan, as an American, would ultimately win, especially against the explicit stand-ins for those nationalistic fears, like Nikolai Volkoff or the Iron Sheik. His appeal then was not in winning but in appearing to almost lose.

A DECADE EARLIER, the French semiotician Roland Barthes opened his Mythologies with one of the first academic appraisals of this phenomenon: “The function of the wrestler is not to win, it is to go exactly through the Kabuki of what is expected of him.” In Hogan’s case, this was epitomized by “hulking up,” his ritualistic dance that signified the beginning of a match's third act.

It goes like this: Having recently escaped from a pin or been knocked down by an attack, Hogan gets up from the ground shaking both fists, his face almost purple with rage. His opponent punches him, though Hogan completely ignores this. He reacts to a second punch, but not out of pain.

He is clearly beyond all sensation now.

Instead, Hogan straightens up, points to his opponent, and slowly wags his finger in admonishment. The crowd is livid with a combination of excitement and nostalgia, having waited all night to see this exact sequence of events for the hundredth time.

Fully hulked up, Hogan is now invincible, impossibly strong, and destined to win within the next few seconds. He blocks his opponent’s next punch, punches back three times, whips him into the ropes, and knocks him down with a high kick on the rebound. Atomic leg drop. 1-2-3! The crowd cheers. Hogan’s “Real American” theme song plays.

After a decade of reaping the rewards of this dance, Hogan was put at the forefront of the early ’90s steroids scandal that required the WWF to admit its scripted nature and soon defected to its main rival. He would spend the 20 years bouncing back and forth between the WWF and its competitors, turning heel as necessary so crowds would cheer even louder when the pendulum inevitably swung back to face.

Each time he returned, he was a little slower. A little balder. The penultimate kick drifted from the face to the chest to the gut, the half-life of the atomic leg drop waned. Now pushing 60, his wrestling repertoire has become extremely limited compared to the high-flying 20-somethings he trades headlocks with. Jaded fans consider him a joke, desperately clinging to his past glory. But even they are not immune to the charms of the one move Hogan will do far past the day his body is too shattered to climb to the top of a turnbuckle: the hulk-up. They cheer along with the rest of the crowd, and yell, “You!” when he points his finger.

BARTHES’ CRITICS SAY his conception of wrestling as a series of barely connected scenes, with each move or hold its own passion play, no longer applies to the modern soap opera that tells story arcs over the course of years. But just as all matches have the same basic script, all of these stories are of the same Ur-story, cyclically playing themselves out. The cumulative effect is to trap certain tropes, characters, motions, and emotions in a timeless tableau, like a spinning propeller whose blades appear to be standing still.

The wrestling industry survives through these self-contained mythologies, distilling all of the unpredictable conflicts from real sports—or the real world—into their most pure and perfect forms. Hogan survives on it, too. Hulking up may well be the platonic ideal of the comeback. Paradoxically, it resonates with the audience not because it is unlikely but because it is inevitable. He has created a kind of perpetual emotion machine: the rising hero forever suspended in the moment before his triumph.

One of the highlights of this year’s AAAS meeting (at least to someone following online) was a session called “Watching the Watchmen and Cheering the Heroes: The Science of Superheroes.” At its core was a panel moderated by Jennifer Ouellette, director of the Science and Entertainment Exchange, or SXE, an organization that aims to “bridge the gap” between fiction and non-fiction. Writers and directors get help on source material from scientists, who in turn have an opportunity to connect their areas of expertise with general audiences. 

Of the panelists, the one who made the biggest impression outside the science community was Sidney Perkowitz, a physics professor at Emory and a member of SXE. In an effort to bolster the public’s understanding of science and respect for scientists, Perkowitz has developed a highly quotable rule of thumb for their depiction in cinema: “one big scientific blunder in a given film.”

Of course, this rule could be seen as an example of science’s public relations problem. From an insiders’ perspective, this is a professional defending his turf from exploitation and perversion. But from an outsider’s perspective, this is an egghead who only deigns to come down from the ivory tower to throw a wet blanket over the entire concept of fiction. You mean Spiderman catching Mary Jane a second before she hits the pavement would do as much damage as just letting her fall? Where’s the fun in that?

Ouellette gives a recap of the panel at her group blog, Cocktail Party Physics, where she says Perkowitz’s position has been blown out of proportion somewhat. The main idea is consistency and plausibility of the premise, rather than breaking out a protractor every time someone fires a gun, as these guys might. Singled out were the giant bugs of Starship Troopers who would collapse under their own weight, and the instant ice age of The Day After Tomorrow.

Science fiction fans will recognize this as a variant of the “hard versus soft” debate, or as I like to call it, pretty much every conversation I’ve ever had with my colleague Lee Billings. And while I find Perkowitz’s aim of getting the public more interested and knowledgeable about science an eminently laudable goal, as a soft sci-fi devotee, I can’t totally let him off the hook. It seems that he is making two contrary suppositions in his crusade: One, that moviegoers are at risk of being unduly led to believe that the science of the movies is the same as the real world, and two, that moviegoers don’t want to see films that have preposterous relation to real world science.

While those two camps certainly exist, I would imagine that they don’t overlap. I also imagine the second doesn’t include enough people to really influence Hollywood’s decision-making. To wit, Perkowitz’s claim that The Core, a ridiculously implausible movie where Hilary Swank and Aaron Eckhart drill to the center of the planet to save the world from killer sunbeams, “did not make money because people understood the science was so out to lunch.”

The Core made about $74 million; not a huge success, but not a flop either. Compare that to the meager $12 million made by Gattaca, a much better film by any measure and one of Perkowitz’s exemplars of science-done-right cinema.  And though Gattaca succeeded artistically and in scientific plausibility, it wasn’t immune from criticism by geneticists and bioethicists who felt that its extreme vision of genetic discrimination was essentially an anti-science message.

On the other extreme is Avatar, which is now easily the most successful film ever made and nothing one might mistake for a textbook supplement. It’s not alone at the top of the box-office charts, either: about two-fifth’s of the all-time top 50 are obviously science-fiction, with another handful on the border. These big earners include such highly scientifical works such as Independence Day and both Transformers movies. 

But maybe there is hope buried in those statistics. Despite the compound scientific impossibilities inherent in its premise, Avatar is a movie about science, whereasIndependence Day and its ilk are movies about blowing things up. After watching Avatar, one can talk about the scientist’s role in the technological dichotomy inherent to colonialism without getting into the economics of shipping magic rocks four light-years to hit quarterly profit targets. Likewise, as Perkowitz suggests, was The Day After Tomorrowa “teachable moment” on climate change, even if it got the science totally wrong. 

It’s those kinds of movies—or television shows, or video games—that scientists have the potential for the return on investment. But don’t miss the forest for the trees; if it takes giant blue aliens or a glacier crushing New York City to make people watch a movie about ecology, we can work on the details later.