Industrial Physics Forumtag:blogs.physicstoday.org,2008:/industry//52008-10-22T16:31:46ZA blog by science writer Jennifer Ouellette, covering the American Institute of Physics Industrial Physics Forum on "Nanotechnology in Society and Manufacturing" taking place November 12-14, 2006 in San Francisco, CaliforniaMovable Type 3.33Farewell to Bostontag:blogs.physicstoday.org,2008:/industry//5.35342008-10-22T16:25:20Z2008-10-22T16:31:46ZYet another whirlwind Industrial Physics Forum has drawn to a close, and yet again, I found myself frustrated at being unable to write about more than a fraction of the fascinating talks I heard over the course of two-and-a-half days....Physics Todayhttp://physicstoday.org
really regret not getting around to mentioning Edie Widder's fascinating overview of deep sea bioluminescence, particularly why it poses a challenge for planned underwater neutrino detectors. C'est la vie. It's time to wave goodbye to Beantown and head back to sunny Los Angeles. But I'm going with a head stuffed full of great science -- and what could be better than that?
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LIDAR Goes Coast to Coasttag:blogs.physicstoday.org,2008:/industry//5.35332008-10-22T15:25:11Z2008-10-22T16:21:00ZHurricanes wreak havoc not just on manmade infrastructre, but also on coastal shorelines, shifting large amounts of soil (through erosion or accretion) that can dramatically reshape coastlines, sometimes with serious environmental impacts. The US Navy worries constantly about avoiding collisions...Physics Todayhttp://physicstoday.org
There's more than one kind of LIDAR system, and which one to use depends on the application. If you want to map a shallow river bed underwater, or use the system for mine detection, you're better off using differential absorption LIDAR. Underwater imaging in particular can be difficult using infrared and near-infrared preferred for terrestrial mapping, since water absorbs those wavelengths; only the blue-green end of the visible spectrum can penetrate water, for the most part.
Arete's Bruce Hubbard reported at Tuesday morning's IPF session on the development of his company's streak-tube imaging LIDAR (STIL). STIL uses a combination of air and underwater-borne platforms to produce very high resolution 3D images of ocean scenes from a remote platform. In particular, says Hubbard, it enables "unrivaled object detection and classification in turbid media" -- that is, the cloudy waters along coastal shorelines, or especially choppy waves. Arete uses STILL as the basis for its collision avoidance system, which allows high-speed water craft to detect and avoid floating obstacles, shallow bottoms, or submerged (or floating) military mines.
Another speaker at the session, Jennifer Wozencraft, is a scientist with the US Army and LIDAR Bathymetry Technical COE. She has been conducting various surveys around the world using a system developed in the 1980s known as SHOALS (Scanning Hydrographic Operational Airborne Lidar Survey). Applications include shoreline mapping -- important before and after major storm surges like hurricanes to measure any topographical changes like soil erosion or accretion -- as well as mapping coral reefs, nautical charting, and flood water modeling.
Bathymetric LIDAR systems like SHOALS transmit two light waves, one in the infrared and one in the green spectrum, and are capable of detecting two returns that delineate the water surface and seabed. The infrared band is quickly absorbed, so it's perfect for detection on the surface of the water, while the green band is used as the optimum color to achieve maximum penetration in shallow water.
In 2003, Wozencraft began working with a new and improved system, called Compact Hydrographic Airborne Rapid Total Survey (CHARTS), which fused multiple sensors into one remote sensing system to better characterize coastal dynamics and update shallow water charts. Specifically, CHARTS incorporates a hydrographic laser system, topographic laser system and digital camera, with a future option being a hyperspectral imager.
Wozencraft has deployed these systems to map coastlines all over the globe. Her latest project, Coastal Zone Mapping and Imaging Lidar (CZMIL) employs a new state-of-the-art optical system for improved depth measurements, as well as streamlined data processing. The latter is particularly important to fill in key gaps in data -- the result of things like bubbles in breaking waves, or particles of sand stirred up in shallow coastline waters.
But the most striking part of Wozencraft's presentation were her before-and-after LIDAR images of shorelines post-Hurricane Ivan (2004) and Katrina (2005):
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Up, Periscopetag:blogs.physicstoday.org,2008:/industry//5.35322008-10-22T04:04:13Z2008-10-22T04:59:42ZOn February 9, 2001, 9 miles off the south coast of Oahu, Hawaii, a US Navy submarine, the USS Greenville, was demonstrating some fairly routine underwater maneuvers for a group of visitors on board, including a rapid resurfacing after a...Physics Todayhttp://physicstoday.org
Ehime Maru. Its rudder sliced the Ehime Maru's hull from starboard to port, sinking the fishing trawler in five minutes. Nine people aboard were killed, including four high school students and two teachers. The Ehime Maru was a training vessel for students considering a fishing career.
There was a great deal of finger-pointing and blame as a result, and the submarine's captain was reprimanded for what turned out to be an operational error: he and his crew were distracted by their visitors and failed to accurately keep track of the Ehime Maru's position before resurfacing. But while such a thing is rare, it is not unprecedented. These things happen because submarines are at their most vulnerable when surfacing. Stealth is key, so that can't use active sonar to scan for other boats as they resurface, so there's always a point where they're literally just flying blind, just for a minute or so, before breaking the surface.
If only there were a way to provide a passive set of "eyes" capable of scanning the surface from below for nearby boats to get rid of that blind spot without sacrificing the need for stealth, collision avoidance wouldn't be such a major issue. If Bruce Hubbard of Arete Associates succeeds in his quest to build a "virtual periscope," the US Navy will have just that. Arete's system -- still under development -- uses a compact set of sensors and computer algorithms to process the data and correct for the inevitable image distortions caused by waves along the ocean's surface.
Hubbard was on hand this morning at the IFP meeting to discuss Arete's progress to date on the Virtual Periscope (VP) system. It seems like a simple enough concept: just place a passive sensor/camera on top of a submarine to collect all that lovely refracted light playing across the surface and then use advanced imaging techniques to reconstruct those bits of light into a usable image. "The VP system uses the ocean as a lens to give submarines the much-needed ability to image the surface," he said.
Alas, it is an imperfect lens. If ocean waters were always calm, this wouldn't be a problem, but there are often surface ways of varying intensity rippling across the surface, and these cause serious scattering effects.
So Arete turned to computer software to process the raw data into usable imagery, based in part on a program called RenderWorld -- the same software used to enhance critical water-centric scenes in the blockbuster films Titanic and Pearl Harbor. Arete adapted Renderworld to work with two other pieces of software to produce their secret weapon: a three-part algorithm that applies multiple signal processing methods (wave estimation, deconvolution, and matched filtering) to the distorted image to correct for the aberrations.
The critical factor is vertical angular resolution, which is around 30 degrees for the raw images; the optimal goal is 1 degree. This would enable the VP system to detect a 100-foot tall object to about 2000 yards out, or a 50-foot object at about 1000 yards out, sufficient distance for a surfacing submarine to avoid a collision in time.
The algorithm thus far has successfully reduced the vertical angular resolution down to 3 degrees, and early testing provided proof of principle -- enough for the Office of Naval Research to provide much-needed R&D funding. But the successful detection of objects a mere 100 yards out just won't give sub operators enough time to react and avoid a collision.
So what's next? According to Hubbard, one goal is to combine the three software pieces into one integrated technique to further enhance clarity of the processed images. (Adaptive optics, used to correct aberrations in telescope images caused by atmospheric turbulence, cannot be used because it is an active system, and the signal would give away a surfacing submarine's position.)
Ultimately, says Hubbard, the key will be to more precisely map out the topology and dynamics of the ocean's surface, and obtain a better understanding of that constantly changing environment. Right now, the algorithms must make certain critical estimates of conditions before it can process images -- and they are clearly not accurate enough, although enormous improvements have been made in recent years.
If only Arete hadn't lost its federal funding! I guess that makes the Virtual Periscope system the latest victims of draconian budget cuts for science. But I hope Arete finds the funds to continue developing the system. Our submarines clearly need better underwater "eyes."
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Shine On, Coral Reefs!tag:blogs.physicstoday.org,2008:/industry//5.35312008-10-21T18:34:30Z2008-10-21T19:10:03ZRemember a couple of posts ago, when I mentioned the glowing kitties, courtesy of the Nobel-Prize-winning GFP protein, and how it's revolutionizing bio-imaging? GFP was first isolated from a jellyfish, but a substantial fraction of the stuff used in labs...Physics Todayhttp://physicstoday.org
In fact, the ocean environment is filled with light, not just from jellyfish and coral, but also some fish, some shells, bristleworms, and crabs, according to Charles Mazel of Physical Sciences, Inc. in Boston, who spoke this morning about his work on coral fluorescence imaging. He spent years making night-time dives to photograph coral reefs under UV light, armed with little more than an LED flashlight and a barrier filter fitted over his diving mask to block out any ambient light that would otherwise backscatter and ruin the image.
Eventually, with the dawn of the digital camera and the ability to limit exposure times, Mazel discovered that he didn't need to dive in the dark anymore. He realized that the creatures' fluorescence was all happening whenever the flash went off, and focusing on just that moment also removed the ambient light effects, without special shading. Voila! Now he could photograph coral reefs 24/7! In fact, it's something of a hobby for many amateur aquarium enthusiasts, who keep sending Mazel their own stunning pix.
Thanks to advances in fluorescent imaging, scientists are learning a lot more about its significance in the marine environment, according to Mazel, mostly because of the superior contrast and level of detail gained from the technique. It's possible to tell the difference between various species of coral, for example, and between the coral and the symbiotic algae that live inside them, doing their bit to keep the food coming via photosynthesis. Also, "Little things that are difficult to see in natural light in a complex marine environment can be seen quite easily under fluorescence," says Mazel -- things like baby coral polyps, a strong indicator of the overall health of a coral reef.
One question that hasn't yet been answered is what function fluorescence is supposed to play biologically -- although hypotheses abound. Maybe its purpose is to help capture light on behalf of the symbiotic algae so they can more efficiently go about their photosynthetic business, or perhaps it's meant as a sort of "sunscreen" to protect the algae from excess light. Mazel doesn't think either of those is likely -- or at least not exclusive explanations. There's even some evidence that fluorescence could play a role in coral spawning behavior.
Marine organisms most likely fluoresce for lots of different reasons, as Mazel discovered when he took his passion for marine fluorescence to the deep sea. He mounted a UV light on a submersible manned vehicle and descended 3000 feet, where he spotted a fluorescent sea anemone, a lizard fish, and snagged a first look at a fluorescent shark. A manta shrimp with fluorescent spots appeared to use them as part of its threat display -- a defensive maneuver to warn off predators. I wouldn't mess with the manta shrimp if I were a fish, however; aquarium owners know all too well that a manta shrimp will rapidly kill everything else in your tank.
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Catch a Nanoplasmonic Wavetag:blogs.physicstoday.org,2008:/industry//5.35262008-10-21T04:31:59Z2008-10-21T05:13:20Z The above image is a segment of the famed stained glass windows in the medieval Sainte Chapelle on the Ile de la City in Paris, France. It's featured here because Mark Stockman of Georgia State University specifically cited it...Physics Todayhttp://physicstoday.org
The above image is a segment of the famed stained glass windows in the medieval Sainte Chapelle on the Ile de la City in Paris, France. It's featured here because Mark Stockman of Georgia State University specifically cited it as an early example of nanoplasmonics in his talk this afternoon on developing an attosecond nanoplasmonic-field microscope. Apparently, glaziers in medieval forges throughout Europe were the first nanotechnologists, producing colors with gold nanoparticles of different sizes.
In August, scientists at Queensland University of Technology made headlines when they announced that stained glass windows that are painted with nanoparticles of gold purify the air when they are lit up by sunlight. The electromagnetic field of the sunlight can couple with the oscillations of the electrons in the gold particles and creates a resonance which breaks apart pollutant molecules in the air. Maybe that's why the windows were fresh in Stockman's mind.
Plasmons are a surface phenomenon unique to metals. When light strikes a metallic surface -- silver or gold, for example -- it generates electron waves, called plasmons. Plasmon oscillations naturally generate local electric fields, and these become especially strong if the frequency of the excited light approaches the frequencies associated with a phenomenon called plasmon resonances.
(Historical footnote: Robert W. Wood, a physics professor at Johns Hopkins University, first observed these so-called "field emissions" -- charged particles emitted from a conductor in an electric field -- in 1897. This effect became the basis for field-emission microscopes, used to study atomic structure. Wood was also the first person to unwittingly record the energy lost as heat by plasmons skimming along the surface of metals in 1902, although he couldn't explain the effect at the time. It took 40 years for Italian physicist Ugo Fano to provide an explanation: metals are not perfect conductors, as had been previously believed. Fano found that a conducting surface could guide light as a 2D surface wave (which is why plasmons are also known as two-dimensional light). Those waves absorb energy, which explains Wood's anomalous observations of energy loss in the light reflected from metallic surfaces.)
The field of nanoplasmonics seeks to exploit these effects at the nanoscale for various applications, such as extracting light from LEDs and nano-antennae for photodetectors and solar cells. For instance, back in 2003, scientists at Los Alamos Natinal Laboratory developed a device called a "nanoscale flashlight", which is how they learned that gold nanoparticles only absorb light above the plasmon resonance; below that threshold, it actually "transmitted" more light than was shone onto it -- known as the nanoantenna effect.
Nanoplasmonic systems are also great for ultrasensitive sensing and detection. There are already nanoplasmonic-based immunoassays available, and a heart attack test is in clinical trials, as is an HIV test, according to Stockman. Home pregnancy kits are now a mass-market item. Nanoplasmonics also hold promise for a non-toxic thermal cancer therapy; the technique is currently in stage 3 clinical trials.
Of course, this is a tough thing to control at the nanoscale, where materials tend to behave somewhat differently than they would at the macroscale, but recent advances in coherent control and visualization of nanoplasmonics inspired Stockman to pursue an attosecond nanoplasmonic-field microscope (ANFM), capable of non-invasively capturing the ultrafast dynamics of surface plasmons, which tend to unfold in a few hundred attoseconds.
Stockman's method combines photoelectron emission microscopy and attosecond streaking metrology to achieve this, along with spatial resolutions at the nanoscale. According to him, this approach is a valuable new means of probing such ultrafast nanolocalized fields in nanoplasmonic systems, and a boon to existing and potential applications.
Those medieval glaziers would no doubt be astounded to learn what materials science has made of their art. Who knew there could be a link between stained glass windows and advanced cancer therapies?
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Bringing MRI to the Nanoscaletag:blogs.physicstoday.org,2008:/industry//5.35252008-10-21T02:53:22Z2008-10-21T04:02:29ZMany years ago, as a budding young science writer, I attended a press conference at a physics meeting and heard John Sidles of the University of Washington describe a promising new imaging technique: magnetic resonance force microscopy (MRFM). He made...Physics Todayhttp://physicstoday.org
magnetic resonance force microscopy (MRFM). He made a strong case that such a technique was needed, particularly for 3D imaging single biological molecules such as proteins at the atomic level, which can't really be done using more conventional methods like X-ray crystallography. MRFM was pretty much in its infancy at the time, but Sidles' lucid, impassioned championing of it stuck with me all these years.
I don't know what Sidles is up to these days, but the other impassioned scientist at that long-ago press conference was Dan Rugar of IBM Almaden Research Center, and he's been fighting the good fight on behalf of MRFM ever since. Rugar was a featured speaker during this morning's session on bio-Imaging, detailing the progress made to date on MRFM and outlining the challenges that (still) remain. Sidles had said it would take a good 10-15 years of R&D before the technique was ready for prime-time; looks like he was right. But it might just be on the brink of success at long last.
MRFM basically combines the concepts of magnetic resonance imaging (MRI) and atomic force microscopy (AFM) to detect the magnetic signal from electrons in a given sample. Electrons have a property known as "spin," causing it take like itsy-bitsy bar magnet, and either attract or repel the magnetic tip of an ultrathin cantilever made of silicon.
The interaction between the electron spin and the magnetic tip causes the cantilever to vibrate ever so slightly in response. A nearby coil generates a high-frequency magnetic field, causing the electron spin to "flip" back and forth between the "up" and "down" positions, alternating attraction and repulsion, causing the cantilever's frequency to change ever so slightly. This slight change can be measured very precisely by a laser beam (courtesy of an interferometer). The data can then be processed in a computer to produce a final image.
It's a complex system with lots of different pieces, each with its own set of technical challenges. Why is MRFM so necessary? Well, proteins, for example, tend to fold in very complex patterns that directly impact how they function, but to date, researchers have been quite limited in their ability to observe biomolecules (and atoms, for that matter) in three dimensions. In nanotechnology and materials science, the ability to precisely locate specific atoms -- to map a material's structure at the atomic level in 3D -- would give deeper insights into how to tailor them to exhibit preferred properties. (Materials derive most of their unique properties from atomic structure.)
Various incarnations of Rugar's MRFM instrument have been used to image the structure of tobacco mosaic virus and dengue virus, as well as hydrogen molecules in a multi-walled carbon nanotube. In 2004, Rugar's team made a critical breakthrough when they directly detected the faint magnetic signal from a single electron buried inside a solid sample -- a 10 million times improvement over conventional MRI machines used to image organs in the human body. It's still not the desired 3D snapshot of a single atom or molecule, it's a strong proof of principle that MRFM is capable of achieving atomic-scale imaging. His team has also demonstrated one-dimensional imaging of a sample with 24-nanometer resolution.
Among the more enabling advances for bringing MRI to the nanometer scale was fabrication of an ultrasensitive silicon cantilever -- a miniature diving board 1000 times thinner than a human hair capable of vibrating about 5000 times a second, with a powerful magnetic tip. (Rugar has his cantilevers tailor-fabricated by B.W. Chui's group at Stanford University.)
It hasn't been easy to get this far, and daunting obstacles still remain, but Rugar is still optimistic that the ultimate goal can be achieved through perseverance and sheer ingenuity -- and the payoff could be revolutionary if/when that happens. "Throughout history, the ability to see matter more clearly has always enabled important new discoveries and insights," Rugar said of these latest advances back in 2004. "This new capability should ultimately lead to fundamental advances in nanotechnology and biology."
Science is like that most of the time: you grind away at the minutiae year after drudge-filled year, until you finally reach a tipping point and make the Big Breakthrough. It's been a long wait for Rugar, Sidles and their many collaborators. Here's hoping MRFM finds its way into widespread lab use very soon, so they can finally break out the bubbly to celebrate much-deserved success.
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Let It Glowtag:blogs.physicstoday.org,2008:/industry//5.35202008-10-20T18:06:27Z2008-10-20T18:44:42ZThis year's Nobel Prize in Chemistry, announced just a couple of weeks ago, honored three scientists -- Osamu Shimomura, Marine Biological Laboratory (MBL), Woods Hole and Boston University Medical School, Martin Chalfie, (Columbia University), and Roger Y. Tsien, University of...Physics Todayhttp://physicstoday.org
But by far the more critical application of GFP has been its use as a tagging tool in bioscience. By using DNA technology, researchers can now connect GFP to other interesting, but otherwise invisible, proteins. This glowing marker allows them to watch the movements, positions and interactions of the tagged proteins, without disrupting or harming the cell, opening new windows into cellular function. Previously, dyes were injected, violating the cell membrane and limiting studies to larger cells.
Fluorescence microscopy is pretty much the standard workhorse for biological imaging these days, but it has limitations, most notably in its ability to resolve and focus on featres smaller than optical wavelengths. Ergo, there are lots of research groups developing ever-better versions of the basic instrument to overcome these limitations. Harald Hess of the Howard Hughes Medical Institute was on hand for this morning's IPF session on bio-imaging to talk about his new bio-imaging technique, Photo-Activated Localization Microscopy (PALM).
Bio-imaging has two main issues. First is the need for sub-optical resolution mentioned above. Second, it requires a biocompatible means of achieving specificity -- that is, there must be a way to enhance the contrast between different proteins, which otherwise pretty much all look alike. GFP provides that contrast, along with other, subsequently developed photo-activatible fluorescent proteins -- it is the "magic bullet" that makes PALM possible, says Hess.
With PALM, successive sparse subsets of fluorescent proteins like GFP can be activated individually, then excited to cause them to fluoresce so they can then be imaged. And this process can be done repeatedly, accumulating the data to resolve it into a highly detailed PALM image. He's demonstrated the technique on a nice sampling of biological molecules thus far, including mitochrondria, lyosomes, actin networks, and other cell structures.
The next step for Hess and his colleagues is the development of dual color PALM imaging, as well as a related technique combining PALM with an interferometric microscope to measure the vertical position of fluorescent molecules. Dubbed iPALM, this technique can provide fully three-dimensional imaging of proteins with resolutions as small as 20 nanometers. Hess would also like to increase the imaging speed of PALM-based techniques to achieve live cell imaging and motion tracking of molecules, with the aim of directly observing how molecular transport mechanisms work in situ.
Maybe it's not as mainstream media-friendly as glowing cloned kitties, but PALM nonetheless makes some awfully pretty pictures.
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Telescopes: The Next Generationtag:blogs.physicstoday.org,2008:/industry//5.35182008-10-20T02:44:53Z2008-10-20T05:12:17ZEver since a 16th-century eyeglass manufacturer in the Netherlands named Hans Lippershey invented the first telescope, the instruments have been getting bigger. In fact, according to Rebecca Bernstein of the University of Sant Cruz, who kicked off the opening session...Physics Todayhttp://physicstoday.org
Of course, scaling up what has worked for smaller telescopes in the past is no easy feat. Fortunately, the scientists developing the TMT were able to build on past experience with segmented-mirror designs, most notably the famed KECK telescope in Hawaii, which boasts 36 segmented mirrors. In contrast, the TMT will employ 492 hexagonal mirrors, each about 1.44 meters (57 inches) across its corners, arrayed together into a 30-meter-wide primary mirror. The individual segments aren't necessarily much larger, but there are more of them, and they are more aspherical and highly curved, thanks to advances in lens manufacturing techniques.
Other practical considerations: the optics must be finely calibrated, and huge, but also thin and lightweight. Adaptive optics will be needed to correct aberrations caused by turbulence in the atmosphere, so the TMT scientists must figure out how to scale up existing AO technologies sufficiently, and implement active controls.
Furthermore, the entire structure must be stable, able to withstand high winds in particular. That's because location matters: the best sites for this next generation of telescopes are high, dry, and generally pretty remote -- which can substantially increase construction costs. Site selection is still underway for the TMT, but Bernstein said that they are looking at areas in Chile, among other regions.
Ultimately, though, the biggest obstacle is that all these technical challenges must be balanced against a corresponding need to control costs. We're talking about capital costs of around $1 billion, amassed from a combination of private and federal funding. Once it's up and running, Bernstein estimates that the TMT will cost around $100 million annually to operate. That's not exactly chump change, and it will need to be squeezed out of federal funding agencies.
And that, says Bernstein, means the astronomy community will need to present a solid consensus to funding agencies on the necessity of what she describes as both "a new technical and cultural frontier for astronomy." Make a convincing case, and scientists will be able to explore when the first sources of light and the first heavy elements in the universe formed, along with galaxies an large-scale structure in the young universe. We will learn more about the massive black holes believed to be at the center of most galaxies, and about the process of planet formation and the properties of extra-solar planets.
Offhand, I'd say that'd be worth a cool $100 million a year.
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IPF08 Comes to Beantowntag:blogs.physicstoday.org,2008:/industry//5.35172008-10-19T18:41:48Z2008-10-20T17:36:51ZBoston, Massachusetts, is primed and ready to host the 2008 Industrial Physics Forum (IPF), held in conjunction with the annual meeting of the American Vacuum Society (AVS). This year's theme is "Frontiers in Imaging: From Cosmo to Nano," with sessions...Physics Todayhttp://physicstoday.org
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If only there were a way to provide a passive set of "eyes" capable of scanning the surface from below for nearby boats to get rid of that blind spot without sacrificing the need for stealth, collision avoidance wouldn't be such a major issue. If Bruce Hubbard of Arete Associates succeeds in his quest to build a "virtual periscope," the US Navy will have just that. Arete's system -- still under development -- uses a compact set of sensors and computer algorithms to process the data and correct for the inevitable image distortions caused by waves along the ocean's surface.
Hubbard was on hand this morning at the IFP meeting to discuss Arete's progress to date on the Virtual Periscope (VP) system. It seems like a simple enough concept: just place a passive sensor/camera on top of a submarine to collect all that lovely refracted light playing across the surface and then use advanced imaging techniques to reconstruct those bits of light into a usable image. "The VP system uses the ocean as a lens to give submarines the much-needed ability to image the surface," he said.
Alas, it is an imperfect lens. If ocean waters were always calm, this wouldn't be a problem, but there are often surface ways of varying intensity rippling across the surface, and these cause serious scattering effects.
So Arete turned to computer software to process the raw data into usable imagery, based in part on a program called RenderWorld -- the same software used to enhance critical water-centric scenes in the blockbuster films Titanic and Pearl Harbor. Arete adapted Renderworld to work with two other pieces of software to produce their secret weapon: a three-part algorithm that applies multiple signal processing methods (wave estimation, deconvolution, and matched filtering) to the distorted image to correct for the aberrations.
The critical factor is vertical angular resolution, which is around 30 degrees for the raw images; the optimal goal is 1 degree. This would enable the VP system to detect a 100-foot tall object to about 2000 yards out, or a 50-foot object at about 1000 yards out, sufficient distance for a surfacing submarine to avoid a collision in time.
The algorithm thus far has successfully reduced the vertical angular resolution down to 3 degrees, and early testing provided proof of principle -- enough for the Office of Naval Research to provide much-needed R&D funding. But the successful detection of objects a mere 100 yards out just won't give sub operators enough time to react and avoid a collision.
So what's next? According to Hubbard, one goal is to combine the three software pieces into one integrated technique to further enhance clarity of the processed images. (Adaptive optics, used to correct aberrations in telescope images caused by atmospheric turbulence, cannot be used because it is an active system, and the signal would give away a surfacing submarine's position.)
Ultimately, says Hubbard, the key will be to more precisely map out the topology and dynamics of the ocean's surface, and obtain a better understanding of that constantly changing environment. Right now, the algorithms must make certain critical estimates of conditions before it can process images -- and they are clearly not accurate enough, although enormous improvements have been made in recent years.
If only Arete hadn't lost its federal funding! I guess that makes the Virtual Periscope system the latest victims of draconian budget cuts for science. But I hope Arete finds the funds to continue developing the system. Our submarines clearly need better underwater "eyes."
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Thanks to advances in fluorescent imaging, scientists are learning a lot more about its significance in the marine environment, according to Mazel, mostly because of the superior contrast and level of detail gained from the technique. It's possible to tell the difference between various species of coral, for example, and between the coral and the symbiotic algae that live inside them, doing their bit to keep the food coming via photosynthesis. Also, "Little things that are difficult to see in natural light in a complex marine environment can be seen quite easily under fluorescence," says Mazel -- things like baby coral polyps, a strong indicator of the overall health of a coral reef.
One question that hasn't yet been answered is what function fluorescence is supposed to play biologically -- although hypotheses abound. Maybe its purpose is to help capture light on behalf of the symbiotic algae so they can more efficiently go about their photosynthetic business, or perhaps it's meant as a sort of "sunscreen" to protect the algae from excess light. Mazel doesn't think either of those is likely -- or at least not exclusive explanations. There's even some evidence that fluorescence could play a role in coral spawning behavior.
Marine organisms most likely fluoresce for lots of different reasons, as Mazel discovered when he took his passion for marine fluorescence to the deep sea. He mounted a UV light on a submersible manned vehicle and descended 3000 feet, where he spotted a fluorescent sea anemone, a lizard fish, and snagged a first look at a fluorescent shark. A manta shrimp with fluorescent spots appeared to use them as part of its threat display -- a defensive maneuver to warn off predators. I wouldn't mess with the manta shrimp if I were a fish, however; aquarium owners know all too well that a manta shrimp will rapidly kill everything else in your tank.
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Of course, this is a tough thing to control at the nanoscale, where materials tend to behave somewhat differently than they would at the macroscale, but recent advances in coherent control and visualization of nanoplasmonics inspired Stockman to pursue an attosecond nanoplasmonic-field microscope (ANFM), capable of non-invasively capturing the ultrafast dynamics of surface plasmons, which tend to unfold in a few hundred attoseconds.
Stockman's method combines photoelectron emission microscopy and attosecond streaking metrology to achieve this, along with spatial resolutions at the nanoscale. According to him, this approach is a valuable new means of probing such ultrafast nanolocalized fields in nanoplasmonic systems, and a boon to existing and potential applications.
Those medieval glaziers would no doubt be astounded to learn what materials science has made of their art. Who knew there could be a link between stained glass windows and advanced cancer therapies?
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It's a complex system with lots of different pieces, each with its own set of technical challenges. Why is MRFM so necessary? Well, proteins, for example, tend to fold in very complex patterns that directly impact how they function, but to date, researchers have been quite limited in their ability to observe biomolecules (and atoms, for that matter) in three dimensions. In nanotechnology and materials science, the ability to precisely locate specific atoms -- to map a material's structure at the atomic level in 3D -- would give deeper insights into how to tailor them to exhibit preferred properties. (Materials derive most of their unique properties from atomic structure.)
Various incarnations of Rugar's MRFM instrument have been used to image the structure of tobacco mosaic virus and dengue virus, as well as hydrogen molecules in a multi-walled carbon nanotube. In 2004, Rugar's team made a critical breakthrough when they directly detected the faint magnetic signal from a single electron buried inside a solid sample -- a 10 million times improvement over conventional MRI machines used to image organs in the human body. It's still not the desired 3D snapshot of a single atom or molecule, it's a strong proof of principle that MRFM is capable of achieving atomic-scale imaging. His team has also demonstrated one-dimensional imaging of a sample with 24-nanometer resolution.
Among the more enabling advances for bringing MRI to the nanometer scale was fabrication of an ultrasensitive silicon cantilever -- a miniature diving board 1000 times thinner than a human hair capable of vibrating about 5000 times a second, with a powerful magnetic tip. (Rugar has his cantilevers tailor-fabricated by B.W. Chui's group at Stanford University.)
It hasn't been easy to get this far, and daunting obstacles still remain, but Rugar is still optimistic that the ultimate goal can be achieved through perseverance and sheer ingenuity -- and the payoff could be revolutionary if/when that happens. "Throughout history, the ability to see matter more clearly has always enabled important new discoveries and insights," Rugar said of these latest advances back in 2004. "This new capability should ultimately lead to fundamental advances in nanotechnology and biology."
Science is like that most of the time: you grind away at the minutiae year after drudge-filled year, until you finally reach a tipping point and make the Big Breakthrough. It's been a long wait for Rugar, Sidles and their many collaborators. Here's hoping MRFM finds its way into widespread lab use very soon, so they can finally break out the bubbly to celebrate much-deserved success.
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