Spatial analysis of cold-water coral and cold seep distributions in the Gulf of MexicoThis is where you will be able to read the text from my conference poster. Please leave comments if you have any questions about or suggestions for my research!
Background The deep Gulf of Mexico is home to numerous cold seeps and cold-water coral communities that are found within close proximity to one another.1,2 The goal of this project was to characterize the fine-scale habitat changes that occur between these two distinct communities. The chemical environment produced by seepage from the seafloor alters the local water chemistry in was that can affect coral habitat suitability. The seep microbial community produces authigenic carbonate rocks that facilitate coral settlement, but only after the negative effects of seepage (toxic hydrogen sulfide, hydrocarbons, and lower dissolved oxygen) have declined or ceased.3 Methods 1. AUV Sentry was deployed at nine sites across the northern Gulf of Mexico, measuring water chemistry within 5m of the seafloor and taking downward-looking photos. 2. Photos were visually assessed and scored for presence or absence of the following:
Results
Discussion Dissolved oxygen was hypothesized to be a limiting factor for coral distributions, but it was not significantly correlated within these sites. This may be due to GoM cold-water corals living in lower oxygen conditions than conspecifics in other oceans.4,5 Local coral habitat is most constrained by the presence of hard substrate to settle on, and the chemical influence of seepage also showed the hypothesized negative correlation to coral distribution in most cases. Future Directions
1. Cordes, E. E., McGinley, M. P., Podowski, E. L., Becker, E. L., Lessard-Pilon, S., Viada, S. T., & Fisher, C. R. (2008). Coral communities of the deep Gulf of Mexico. Deep Sea Research Part I: Oceanographic Research Papers, 55(6), 777–787. http://doi.org/10.1016/j.dsr.2008.03.005 2.Cordes et al. (2009) Annual Review of Marine Science 3.Liebetrau et al. (2010) Marine Geology 4.Lunden et al. (2014) Frontiers in Marine Science 5.Georgian et al. (2016) Limnology and Oceanography 6.Quattrini et al. (2013) Molecular Ecology Acknowledgements This work would not have been possible without funding from the NSF Ocean Acidification program, the crew of the 2014 R/V Altantis cruise, and the scientific AUV Sentry team.
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Quick, what's the one piece of technology in the Iron Man saga that you want the most? If you said "Powersuits!" you're thinking small, my friend. Why not ask for the computer program that can build powersuits for you?? I am of course referring to the artificially superintelligent computer system known as J.A.R.V.I.S. Just look at the work Tony Stark does and think of how much more quickly you could design robots with that kind of software: Jarvis was originally a human butler in the Iron Man comic mythos. You could say he was the Alfred of the Marvel universe for the Stark family. After Edwin Jarvis's death, Tony Stark created an artificial intelligence system integrated into his home and powersuits called J.A.R.V.I.S. In a convoluted name worthy of its British-ness, J.A.R.V.I.S. was said to be an acronym for Just A Rather Very Intelligent System. There are so many cool features about this computer system that can think, build fantastical machines, and instinctively call your girlfriend when you're afraid you're about to die. One of the greatest, I think we can all agree, is the seamless user interface between Tony's body and J.A.R.V.I.S. And thanks to new technology, we're getting closer to breaking down those barriers and reaching into the computer! There is another sci-fi interface system that eliminates intermediates like mice and keyboards, but still doesn't break all the way through the monitor. Remember the video-viewing system the Pre-Crime Unit used in Minority Report? If you thought that looked like a pretty real, stream-lined system, that's because the computer scientist consulting on the film basically used the movie as a product pitch for a new user interface (and did it more subtly than Lexus did). John Underkoffler and his team didn't go halfway when designing futuristic computers. To enhance the believability of the interface, they developed an entire language of gestures beyond what would be used in the scenes. Even that little glitch where Tom Cruise goes to shake Colin Farrell's hand and accidentally minimizes what he's looking at was a purposeful mistake to show how natural and responsive the system was. Watch Underkoffler demonstrate his gestural user interface and some other novel technologies for integrating computer displays into physical space in this TED Talk: It's always a pleasure to watch science fiction movies and realize how close we are to commercializing such incredible technology. Computer systems are usually one of the most instantly gratifying of these phenomena because the field is progressing at such a rapid pace. Who knows what kind of amazing 3D system we'll be using soon to waste time on the internet! Oh,and if the gloves looked at all familiar, it's because they hearken back to a more ancient technology from a more laughable movie: One scientific aspect that is glossed over too often in superhero stories is the energy required to perform amazing acts. Athletes and body builders with strictly high calorie, high protein diets can tell you that super strength and speed don't come without costs! Many of the powers demonstrated by beloved characters would be impossible without one additional ability: super eating. Let's cut the writers some slack, it would be boring if any movie or show included too much everyday stuff like sleeping and eating, even though that's what people realistically spend most of their time doing. But some good entertainment does take a moment to acknowledge the necessity of super nutrition. For example, the Justice League cartoon frequently makes references to the Flash's abilities to eat as fast as he can do everything else. Unfortunately they don't mention that everyone else on the team would have to eat just as much! Green Lantern has a power ring as a primary energy source, and Batman has upper-range human abilities, but both of them would still have to chow down frequently to maintain their crime-fighting shape. The only exception might be Superman if he really can perform photosynthesis. Although he would still need to consume plenty of nutrients for the raw materials for said synthesis. What they really needed in their Watchtower satellite headquarters was a live-in team of chefs and 24-hour buffet! So how much would the Flash have to eat to run as fast as he does? Again I’m going to borrow some mathematical expertise from James Kakalios’ The Physics of Superheroes in calculating the Flash’s metabolic requirements for super speed. It’s well known that the Flash can run at velocities close to the speed of light, so Kakalios uses a conservative example of 1% of the speed of light to estimate his kinetic energy given a body mass of 70 kilograms. The total comes to a whopping 75 billion Calories/kilocalories! That adds up to 136 million Big Macs, so Barry Allen needs to eat constantly at the same rate he runs. What it comes down to is that the Flash is physically impossible. The comics explained this by saying the Scarlet Speedster’s powers allow him to tap into the “Speed Force” to provide the excess energy needed for his antics. Use the Force, Flash! Now I’m going to add some calculations of my own modeled after the summer blockbuster Iron Man 3. One of the biggest factual holes in the plot was how the Extremis villains were capable of regenerating so quickly AND having enough energy to create searing heat on top of that. Sure, all cellular work has some waste energy lost as heat, but this is ridiculous! The example easiest to calculate for is the scene where Aldrich Killian forces Colonel Rhodes out of the Iron Patriot suit by heating it up. Let's start by assuming that the metal of the suit gets close to its melting point before it triggers the safety release. I'm going to say that about 15kg of the suit material gets heated to that degree since Killian is just focusing on the abdominal area, and from there we can use the specific heat and melting point of the metal it's made of to calculate and approximate amount of energy required to accomplish the feat. What if the Iron Patriot was really made of iron? Iron has a specific heat of 0.108 kcal/kg/°C, so that's how many Calories are required to raise the temperature of one kilogram of iron by one degree Celcius. Now we can calculate that to raise iron from room temperature (20°C) to its melting point (1,538°C) it would take 2,459 kcal! That's more than most people consume in one day and he just blew it in 5 minutes. That is if that heat transfer process was 100% efficient (spoiler alert: it's not). Still, he can make up for it with a believably large lunch of 2 Big Macs, 2 large fries, and a large Coke to wash it all down. This is still a conservative estimate, however, since the Iron Patriot is probably made out of something stronger. Like say, titanium. (Well, a titanium alloy actually, but let's stick to simple elements.) With a specific heat of 0.125 kcal/kg/°C and a melting point at 1,668°C, Aldrich needs a modest 3090 Calories to open up the suit. To cover that cost, he'll need to take a trip to Outback Steakhouse and eat one and a half bloomin' onions! Gross right? The last calculation I'll make is purely for fun: what if Rhodey's suit was hilariously made up of Rhodium? This would be a poor choice as it's a less sturdy metal. It's specific heat is only 0.058 kcal/kg/°C, but with a melting point at 1,963°C there's some distance to cover. The total comes to 1,690 Calories, so at least that's within range for normal human consumption. The main point is that a whole day's worth of food is burned up in a few minutes, and then these guys keep doing even more extraordinary fire acts throughout the movie! It's just not feasible without them refueling in between every superheated punch. Okay, so the powers of the Extremis virus were definitely exaggerated. It comforts me to know that there are some physical laws that prevent scientists from turning people into human bombs accidentally. But the idea of using a virus to alter organisms' DNA? That's totally legitimate! These Hollywood people hire science consultants to make sure they don't get everything wrong. The NAS's Science and Entertainment Exchange did work on Iron Man 2 and other Avengers-related movies, but I can't find a specific scientist credit for Iron Man 3. Now that you know that most superheroes are metabolically impossible without a fictional miracle exception, there are two ways to cope with this letdown.
For example, when Captain American is feeling down in his eponymous film after losing his good friend Bucky, he hides himself in the rubble of a former bar and fails to drink his worries away because he metabolizes the alcohol too fast to feel the effects. I like to imagine that he only turned to liquor after rummaging around for abandoned food to satisfy his unending hunger! The next time you see a big elaborate hideout, think to yourself: "Where's the food?" Wayne Manor doesn't have a lot of staff (or probably any) besides Alfred, so Batman probably doesn't have a team of chefs. But what if he used his gadget powers to build a breakfast-making machine that could be operated by one person? Every eccentric genius has one of those! Going back to Iron Man 3, it makes a lot of sense that in addition to all the other luxuries they had to make the Mandarin's mansion nice and comfy there would be an army of cooks pumping out food for all of the Extremis gang. And I know we see a lot of the helicarrier in The Avengers, but I would bet that the unseen sections are as large of kitchens as can be made airborne. What happens when the heroes are out adventuring? Utility belts can hold more than just weapons and toys. They're probably chock full of granola bars and trail mix! When you get to skintight costumes the thought exercise becomes more challenging. You can either think of really creative ways that the hero hides food on their person or admire their excellent foraging skills in adverse situations. I sincerely hope this game enhances your next viewing experience!
This is the last one, I promise! Heat vision: I always thought this was a ridiculous power that couldn't possibly happen in real life, and that's still the case. Sorry! The movie was slightly more realistically satisfying in demonstrating a steep cost for Superman's heat vision. It consumed a lot of energy and appeared to momentarily blind him. So watching this movie was less frustrating than watching the (excellent) Justice League cartoon show where you just want to shout at Superman “Stop punching him and use your freaking eye lasers!” I guess that would have ended every conflict too quickly... To make up for any disappointments, here's some bonus science accuracy! In the scene where they find a crashed Kryptonian ship in the ice in the Arctic, scientists there say that they dated approximately how old it is (it's been buried more than 20,000 years) according to the stable isotope composition of the ice cores taken from around it. This is absolutely how science works! The stable isotope composition of the atmosphere changes in predictable annual cycles, as well as in large trends seen over thousands of years. When tiny gas bubbles get frozen in ice, they become a historical record of what the ancient atmosphere was like. Usually it is the ratio of heavy oxygen atoms (δ18O) to normal lighter oxygen atoms that is measured for a signature. Another science bonus related to the Man of Steel is an update on our progress towards X-Ray vision as discussed in Part II. Scientists have done something cool (and a little crazy) in the field of enhancing perception. Using technology similar to the tools we use to restore hearing to the deaf with cochlear implants or visual stimulation to give blind individuals basic sight, these researchers asked the question "Can we extend this stimulation beyond the normal range of perception?" To answer it, they attached headgear to adult rats. The tech consisted of a device that could sense infrared light (invisible to rats and humans alike) and a circuit to transfer this signal directly into the rat's brain where it would register as a sensation on its whiskers. The rats had previously been trained to choose among a number of ports in an experimental set up based on visible light cues from an LED light where the lit port provided a reward of water. After installing the electrodes in their brains, the researchers took away the visible light and gave the rats IR light cues to figure out which port held the reward. It took the rats a few weeks to figure out why their whisker senses were tingling, but they learned to detect the IR and navigate towards it repeatably. So they weren't "seeing" IR per se, but they were certainly sensing a form of radiation that had previously been imperceptible! References:
Thomson, E.E. et al. Perceiving Invisible Light through a Somatosensory Cortical Prosthesis. Nat. Commun. 4:1482 doi: 10.1038/ncomms2497 (2013). Another source of Kal-El's power is the energy and rejuvenation he receives from Earth's yellow sun. This is a little shaky scientifically, but let's explore some possibilities of super sunlight. To start, is there any truth behind the idea that Earth's sun is more energy-rich than Krypton's? That's stated as another reason why Superman is more powerful than his people were at home. After consulting astronomical expert Nicole Bardy*, I found that there is indeed some evidence for this! When stars are very young, their radiation output is faint. As they grow and enter a stage of their life called the Main Sequence, their radiation increases. This stage takes up ~90% of their lifetime. Towards the end of their lifespan they become red giants, whose luminosity decreases. Right now our sun is in its Main Sequence and Krypton's sun has been described as a "red sun" in the comic books. This data supports Jor-El's claim that Earth's younger sun will strengthen his son with its higher levels of radiation! Now we get to the trickier part of explaining biologically why this increased radiation is beneficial to our hero. The first thing that comes to mind when discussing solar boosts is photosynthesis. Could Superman have some photoactive compounds that allow him to harvest energy from sunlight? Although Kal-El isn't plant-like, humans have been known to photosynthesize at least one substance: vitamin D. Vitamin D can be obtained from the diet, but the majority of the compound found in our bodies has been synthesized cutaneously. When human skin is exposed to sunlight, the ultraviolet radiation changes 7-dehydrocholesterol into previtamin D3. The previtamin D3 substance then undergoes a heat-driven transformation into true vitamin D. A more familiar skin response to sunlight is tanning (or burning for pale people). Tanning is a result of another synthesis that is photo-driven. UV radiation incident on DNA and melanocyte membranes triggers a series of reactions that produce the pigment melanin, darkening the skin. While humans technically can photosynthesize, too much radiation quickly becomes a bad thing. After all, the melanin production response is a defense to prevent UV from penetrating your skin again. And what about other kinds of radiation? The stories you hear about any radiation exposure are almost invariably bad. Too many rays lead to DNA mutations that cause cancer, and even the controlled radiation we use in chemotherapy to cure said cancer has terrible side effects. And as Nick Fury put it, even low levels of gamma radiation "can be harmful." So how can any living creature (in our scientific universe) benefit from regular massive doses of radiation? Well there is one Earthly example. In the aftermath of the 1986 Chernobyl meltdown, a large number of black fungi were found thriving in the area. These fungi are darkly-colored because of the same compound mentioned before: melanin. But in the case of Wangiella dermatitidis, Cryptococcus neoformans, and Cladosporium sphaerospermum, they use their melanin as an energy-absorbing pigment similar to chlorophyll's function in plant's photosystems. These fungi are gaining energy from the radiation and turning it into food! The fungi were experimentally grown in melanized and albino strains and their growth measured in the presence and absence of radiation. The melanized fungi grew more in the presence of radiation. And when I said they were found near Chernobyl, I mean they were found growing on the walls of the damaged reactor. These things are so amazing they're talking about growing them in space for astronaut chow because they'll love all the cosmic radiation! Suddenly Superman's sun-based powers are looking more realistic! The melanin-synthesis would have the added benefit of supplying energy for his crazy-high metabolism without requiring him to constantly consume food. Only two questions remain in my mind about this solar-powered phenomenon. 1) Why is he drawn so pale when he could be drawing energy from dark melanin? 2) Why did he build his fortress of solitude above the Arctic Circle where the sun doesn't shine for days at a time?? *Nicole Bardabelias, Cornell University class of 2014, Planetary Science and Astronomy, French horn extraordinaire. References:
Ann R. Webb, Who, what, where and when—influences on cutaneous vitamin D synthesis, Progress in Biophysics and Molecular Biology, Volume 92, Issue 1, September 2006, Pages 17-25, ISSN 0079-6107 Gilchrest BA, Park HY, Eller MS, Yaar M., Mechanisms of ultraviolet light-induced pigmentation, Photochem Photobiol, Volume 63, Issue 1, January 1996, Pages 1-10 Dadachova E, Bryan RA, Huang X, Moadel T, Schweitzer AD, et al. (2007) Ionizing Radiation Changes the Electronic Properties of Melanin and Enhances the Growth of Melanized Fungi. PLoS ONE 2(5) The next talent on the list is Superman's X-Ray vision. I always thought this was a ridiculous power that couldn't possibly happen in real life, but several biological examples, the cinematography of the movie, and a recent class I took about satellites and remote sensing has changed my mind completely. You just need to suspend your disbelief for a few minutes and assume that Kryptonians have evolved to have retinal cells that respond to nearly every wavelength of electromagnetic radiation. I'll lead in with some Earthly examples that show this to be biologically possible. First, bees have an extended visual spectrum that allows them to actually see UV light. We've named this color "bee purple," and plants have evolved together with the bees to take advantage of another visual cue they can use to attract pollinators. In the picture of a cucumber flower below, the left image is what we see, and the right image is a false-color composite of approximately what the bee sees. The bees have a slight trade-off in that they can't see as far into the red end of the spectrum as humans can. The mantis shrimp, on the other hand, compromises nothing! Well, that's a little bit of an exaggeration. They also don't see as well in the red end of the spectrum since that is the first wavelength absorbed by water, but have been found to adapt their vision when raised in shallower environments. They have a complicated vision system that may reach far beyond human eyesight nonetheless. Humans have 4 kinds of photoreceptors in our retinas (rods and 3 colors of cones). Mantis shrimp have 16. We can't even imagine what they see! The shrimp see many colors we can't detect, but due to their smaller invertebrate brains they can't actually tell apart colors as closely as we can. They just group light stimuli of several wavelengths into a single category like one shade of green if that group of receptors is activated. Still, this is an amazing sensory system which I'm sure leads them to appreciate their colorful appearance. Additionally, mantis shrimp have incredibly strong limbs that they use to crack mollusk shells (no easy task as anyone who tried to eat a closed clam can tell you). These punching pincers snap with the speed and force of a gunshot, which is so fast that it momentarily boils the water near them and creates heat and light! They are sounding more and more like Superman... Their power is only exceeded by the similarly pugilistic snapping shrimp. Another animal that takes more advantage of the electromagnetic spectrum for locating food is the pit viper. These snakes are so named for the pits below their eyes that sense infrared radiation. So no, these sensors aren't actually retinal, but they are integrated well enough into the brain that the viper can use this extra sense to find its prey. In some cool research going on at the Grace laboratory at the Florida Institute of Technology, they are blindfolding the snakes to get a better measure of their heat-sensing accuracy. Those are the biological limits of electromagnetic sensing, but mechanically we have come much further in extending our range of "sight." X-ray machines, heat sensors, and satellites take advantage of different wavelengths of radiation to give us another point of view. The advantage of using different wavelengths of light is that we can "see" deeper than the surface of an object. X-rays that look at our bones are the best example of this, and it's usually what you see Superman doing with his heightened senses: looking through surfaces. Different wavelengths can also show differences between objects that can't be seen in only visible light. The infrared heat-sensing image below shows a stark contrast between the warm-blooded human hand and room temperature lizard. We can easily distinguish humans from lizards in the light, but IR vision becomes more valuable in the dark. It's also useful when trying to tell apart objects that appear the same visually. There was an episode of Buffy the Vampire that showed members of the high-tech secret government organization called "The Initiative" using a heat sensor to pick out cold-blooded vampires from crowds of normal humans because outwardly they look the same. Well, as normal as you can be when you live on a Hellmouth... IR spectra are also handy for picking out differences in vegetation, like different crops, the health and moisture content of plants, or AstroTurf vs. real grass. In the left photo of the University of Wisconsin, Madison stadium, the football field is indistinguishable from the green grass and trees of the area. The right image, however, is a false-color composite where high IR reflectance is displayed in red (plants reflect a lot of IR so that they don't heat up). The trees and grass light up in red, but the turf of the stadium remains dark, showing us that it's not planted with real grass. One of the coolest applications of "seeing" other electromagnetic wavelengths would be if Superman could see radio waves. Then he would literally have radar! This suddenly makes his reckless flying through clouds seem much less reckless when you realize that he knows exactly what's on the other side since his radar vision penetrates the atmospheric moisture. So why was he de-powered when dragged into a ship with Kryptonian atmosphere? Why did Zod become overwhelmed with all of these super-senses only when his breather helmet broke and he was exposed to Earth's atmosphere? This can also be explained through the science behind satellites! Satellites are limited to using wavelengths of light that can easily penetrated the planet's atmosphere, especially since the signal has to travel through this boundary twice: first to reach the Earth's surface, then to bounce up to the satellite. Here's a diagram of what parts of the spectrum are the most absorbed by the atmosphere: It is no coincidence that the range we can see, visible light, is also one of the ranges least absorbed by our atmosphere. Animal eyes evolved to take advantage of this abundant, but not very damaging, radiation. So now I'm going to take the evolution proposition from before one step further: Kryptonians came from Earth, but then developed on a different planet where their eyesight had to evolved to see beyond visible light because it didn't penetrate very well, and only after that did they move on to colonize Krypton. On Krypton, the atmosphere was very dense, and blocked out almost everything except visible light. So the enhanced sight that had previously evolved became a vestigial trait that wasn't used until Kal-El came to Earth where more radiation was visible to him. This is a good explanation for his super hearing as well. If Krypton had a dense atmosphere, it is possible that sound didn't propagate very well, and hearing senses had to be more acute to pick up anything.
What I really enjoyed about the movie was Clark's struggles as a child to understand and control these enhanced senses. He has the equipment to see any wavelength of light, but he doesn't know how to focus it on just one part of the spectrum. Hence his vision becomes muddled with overlapping images of his skin, his bones, and his thermal signature all at once. It's an overwhelming experience for any kid! My only scientific qualm with the vision examples used in the movie is the trick he did of reading someone's ID badge through a one-way mirror AND through his pocket. Seeing people on the other side of the mirror would have been easy with IR or X-rays, but unless the name on the badge is written with a radioactive tracer or something special, there's no way Clark should have been able to read it. The letters are only distinguishable with visible light, and those wavelengths simply will not propagate through cloth or mirrors. Nice try, alien. I'll start by saying that I really enjoyed watching the new Man of Steel movie! It was a very immersive experience, and I thought the character of Superman was explained better both physically and psychologically than previous adaptations had done. So the next series of posts are going to be a breakdown of how some of his amazing power can be made possible! Before we start, SPOILER ALERT: Superman saves the day! Let's start with his most obvious feature: super strength. For this, I'm going to cite James Kakalios' The Physics of Superheroes. He goes through some basic calculations in the first chapter and concludes that the planet Krypton had a force of gravity 15 times greater than that of Earth acting on the inhabitants, so Clark's Kryptonian body is adapted to withstanding much stronger forces than humans usually encounter. The chapter goes further to explain that this increased gravity can be caused by super high density neutron star matter at the core of the planet. Even better, this neutron star core would bring about the instability that caused Krypton to collapse just after baby Kal-El was shot into space! It is reasonable to think that Superman's DNA was wired to build a body with incredibly strong bones and muscles, but some will cite the counterargument of "Use it or lose it" in protest. Sure, Clark probably did not reach his full strength potential at first since his muscles wouldn't have overdeveloped in the weaker gravity field. Still, he would have been born naturally stronger than other kids, and once he realized that he probably started bench-pressing farm equipment to build up his body. What else would you do if you were an awkward super-powered adolescent? The super strength explanation spills over into a discussion of his flight powers. Super strong legs is the only explanation needed for the original Golden Age Superman that was "able to leap tall buildings in a single bound" because that was all he got: one bound. This style of flying is similar to the Hulk's galavanting around NYC in The Avengers. There was a subtle homage to this early Superman description in the Man of Steel movie when Kal-El is first testing the limits of his powers after discovering his true identity. He starts flying by making really really big jumps, but then after a few tries he learns the mysterious "double jump" skill and can change course in mid-air without any solid surfaces to push off of. So yeah, there's not really a good scientific explanation than that, sorry.
Stay tuned for X-ray vision Xplained! UPDATE:My first post about Batman's use of sonar in The Dark Knight talked about the similarities between echolocation and modern sonar used to navigate and locate objects underwater. The fictional application of Batman's sonar tool was the part where every cell phone in Gotham was turned into a receiver that fed into a giant computer to find the Joker. Well guess what? We are that much closer to catching the Joker, citizens! A recent paper designed an algorithm that can use recorded echoes from an array of microphones to measure the dimensions of a room. The figure below shows the set up of microphones in their controlled test area as well as the more complex Lausanne cathedral of Switzerland. What makes this a practical criminal catching tool? First, the microphones don't have to be placed in any specific geometry, you can use whatever arrangement is handiest. Second, it has been hypothesized that this algorithm could be programmed into a cell phone app. This echo algorithm can be applied to design more realistic virtual realities or make teleconferencing sound more natural. It would also be a much faster way to measure the dimensions of a room than physically getting out a tape measure. These dimensions would be useful for architectural planning, forensics, rescue missions, and finding criminals escaped from Arkham Asylum! Or at least right now you can accurately find all the walls of the room they're hiding in, which was a big component of the sonar use in The Dark Knight. Now how do we get that cell phone feed to display in some cool goggles... Interested in trying out the code yourself to start your vigilante career? You can find it available freely online! References:
Dokmanic, I., Parhizkar, R., Walther, A., Lu, Y. M., & Vetterli, M. (2013). Acoustic echoes reveal room shape. Proceedings of the National Academy of Sciences, 1221464110 After a long absence due to qualifying exams and other shenanigans, I'm back to fighting crime! Well, the crime of not knowing all of this cool science. This post is branching out into a completely abiotic phenomenon that almost acts as though it's alive... and will EAT YOU ALIVE. The real-life blob attack happened more than a month back on one of the lakes of Minnesota (they have 10,000 after all, it was bound to happen). The only problem is that this blob is made up of the movie blob's one weakness! It's unstoppable! That's right, it's made of ice. Here's a terrifying video from Mille Lacs Lake that shows a giant ice sheet ruthlessly crawling onto land. It may not look like a fast advance, but if you skip from the beginning to the end of the video I guarantee you will be amazed at how far a mini-glacier can proceed in 7 minutes. What causes such a force of nature to climb right up the shore?? A few things have to fall into place during the winter and spring to bring about ice-jacking. The first part of the process is a wide enough fluctuation in temperatures over the season to cause the ice to grow towards shore. When temperatures drop far below freezing, the ice contracts and cracks form between the pieces of the sheet that pull apart from one another as they shrink. New water quickly fills the cracks and freezes to create a continuous ice cover again. If things warm up to a near freezing temperature after that, the ice expands to its original density, but with new ice formed, it no longer fits neatly over the lake! It creeps little by little up the shore every time this process repeats itself. The temperature variations are amplified if there is no thick snow cover over the ice to insulate it. But was this gradual expansion capable of causing the dramatic movement above (helpfully narrated by Minnesota accents)? No, this ice shove was probably made up of discrete chunks knows as ice floes instead of a single sheet. The secret ingredient that created the blob this past year was high winds! Gusts up to 40 mph pushed these floes in one direction across the lake and were powerful enough to keep nudging it up people's backyards. The friction they meet on land is outweighed by the force of the ice behind them piling up when the front slows down. Ice piles like this have been recorded to grow as high as 12 meters when they meet a sufficient barrier. As the immortal line at 5:55 "It's going right through their f***ing house!!" tells us, this blob means serious business as much as any B horror movie monster from outer space. These things cause tons in property damage and cannot be stopped by most of the walls mere mortals can construct. Some piers and bridges are designed to withstand the pressure of advancing ice, but lake houses and cottages don't stand a chance. Your best hope is to build your house far enough away from the shore, or do some long-term forecasting and sell it before a year like this repeats itself. As tragic as that is, the real science fiction ice-related crime is Mr. Freeze from Batman and Robin. Now that I've mentioned The Gecko's Foot, this is a good time to talk about why this appendage is an icon for cool science and bioinspiration. Why is the gecko so interesting to material scientists? Because it can do this! That photo hasn't been rotated. The gecko is literally sticking to glass upside down, and the best part is that it's barely expending any energy! This is an often sought-after skill among espionage experts. Science is getting closer to making those gloves a reality as we unravel and replicate the gecko's secrets. One of the most alluring properties of the adhesion of gecko toes is that they stay completely dry. There's no goo on their feet and no residue left behind on the surface. This is good for spies that don't want to leave a trace, it's a more solid grip than suction cups, and works on more surfaces than magnets. So what is the mechanism behind this completely clean stickiness? It has to do with physical forces that only work on the nano-scale. The gecko's foot is a much more complex surface when you put it under a microscope. It has rows of lamellae on its toepads that are made up of small hairs, which split off into even tinier setae that end in flat spatulas. Why so many minuscule bristles? As I said, the adhesive forces operate at the nano-scale, so the foot must make as many contact points as possible at this scale. What we see as flat surfaces with our unaided eyes are in fact rugged terrains of peaks and valleys when you zoom in: This densely packed array of setae offers a lot more flexibility to the surface of the foot than normal skin would. All of those teeny hairs can bend and compress until they precisely match the topography of the whatever they're trying to stick to. Once you get lizard and glass into such close contact, a phenomenon known as van der Waals forces takes over. This is an attractive force that exists between all atoms that get within a few nanometers of each other. It's not an excessively strong force, but when it's maximized over a large scale, the power adds up quickly. Van der Waals adhesion was first noticed in the gecko, but it's an important mechanism in many other animals. Hm, what else climbs on smooth, often vertical surfaces... Spiders have structures called scopulae that are similarly made up of tiny bristles. They generally have fewer setae than geckos, however, since there is an inverse relationship between the weight of the animal and the number of hair-contacts needed to support it. A spider is lighter than a gecko, so it doesn't require as much van der Waals force to sustain its adhesion to a surface. The first Spider-Man movie (pictured above) got close to addressing the source of Peter Parker's stickiness correctly, but they just missed the target. One scene shortly after his genetic transformation zooms in on his thumb and shows small hairs with intricate structures emerging from his skin. It's a nice try, but those hairs are too widely spaced apart to have any meaningful nano-scale interactions with the brick buildings of New York City. The movie seemed as though it were going for more of a barb-like projection, but that idea falls short as well. Those spines are far to tiny to maintain enough strength to support a man's weight over such a small surface area. And besides, Peter just covers up his sticky hands with gloves anyway! Not to mention the shoes he wears that thwart any possibility of additional adhesion with his feet. That's why X-Men nemesis and member of the Brotherhood of Mutants villain Toad is a more logically sticky character. Toad's gloves only cover his palms, leaving his adhesive fingers plenty of freedom to van der Waals where they please. His palms would offer added stability, but hilarious experiments with geckos have shown that they have enough excess stick-to-it-iveness in their pads that just a single toe is sufficient suspend their entire body. Amphibians do have a slightly different adhesive style however, and a more wet one. Wet adhesion means that we're not as interested in adapting tree frog toepads into industrial nanomaterials because they require a constant reapplication of fluids, whereas gecko feet are more clean and can operate without a living gecko. Recent research has shown that tree frogs do appear to employ some close contact attractive forces with surfaces. Those hexagonal epithelial cells on its toes provide the same flexibility as gecko setae, but at a slightly larger scale. The wetness comes from the fluid mucus that flows in the channels between those flat-ended pegs. Going back to industrial applications, where is my gecko tape?? Rest assured, engineers are working on it as we speak. Andre Geim has had success in replicating the functional nanostructures of gecko feet and making workable gecko tape. The process still needs to be refined, however, before it can be made on a bigger scale and as durable as the gecko feet themselves. The dream of nearly infinitely reusable and mess-free tape is nearly upon us! In reality, most household tapes are good enough already that we won't be seeing gecko tape in our homes too soon. The medical field will certainly jump at the chance to use a strong, removeable adhesive that doesn't introduce sticky chemicals into the body though. So if gecko tape can be successfully fabricated, would it be possible to make those gloves Tom Cruise is using to climb the Burj Khalifa? Yes! Spiderman can become a reality in the near future. Although while I don't doubt the ability of the gloves to stick to walls, how do you keep said gloves from slipping off your hands...? In the meantime, we've adapted these adhesive And since I mentioned Toad, I need to share with you my favorite superhero science lesson of all time: |
Alanna DurkinExploring the realm of biologically inspired design one superhero example at a time, with some other natural sciences mixed in. Archives
September 2016
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