March Meeting 2012
Nanostethoscope Probes Living Organisms Using Atomic Force Microscopy
Researchers at Clarkson University in New York have developed a way to use atomic force microscopy (AFM) to eavesdrop on insects’ internal workings. The researchers delicately taped insects such as flies, mosquitoes, and lady bird beetles beneath a thin metallic membrane. A small hole in the membrane allowed the tiny tip of an AFM probe to touch the insects’ surface and record the sub-atomic-level vibrational buzz emanating from inside the bugs. The nanostethoscope picked up high-frequency vibrations that the researchers identified as coming from specific organs, for example the 300 Hz hum of a ladybug’s heart. Igor Sokolov and colleagues will discuss how AFM can be used to study the reaction and sensing mechanisms of insects, as well as the team’s new foray into the frontiers of human nanophysiology. They will present the first successful measurements of the surface oscillations of a human finger. The team envisions a day in the future when detailed characterizations of the vibrational signature of healthy organs might help physicians diagnose disease.
Session H1.00007 – Atomic force microscopy as nano-stethoscope to study living organisms, insects
Seeing Through Walls, Earth, and Flesh
Our eyes can detect only a tiny portion of the electromagnetic spectrum, which is unfortunate because there are many things that are better illuminated in the microwave, radio, and other wavelengths that are normally invisible to us. Physicists, however, have been finding ways to produce images with invisible light ever since Roentgen first X-rayed the bones of his own hand more than a century ago. Optical imaging has made great strides over the years, producing stunning applications, including several that will be the subject of talks in session D20: Advanced Electromagnetic Imaging and Remote Sensing: From DC to Daylight. Speakers in the session will describe some of the latest methods for detecting buried munitions (Eugene Lavely, BAE Systems), through-wall imaging with microwaves for urban reconnaissance (Peter Weichman, BAE Systems), optical alternatives for breast cancer diagnosis (Eric Miller, Tufts University), improved methods for radar tracking of ground-based objects (Dan Bliss, Lincoln Lab), and the latest techniques for creating detailed and dynamic geographic maps with synthetic aperture radar (Thomas Kragh, BAE Systems).
Session D20 – Invited Session: Advanced Electromagnetic Imaging and Remote Sensing: From DC to Daylight
Textured Nanostructures for Anti-Icing on Airplanes and Other Surfaces
Ice alters the aerodynamics of airplane wings and drastically reduces the efficiency of wind turbines. Removing it often requires expensive heating systems or labor-intensive application of chemical de-icers. Nanoscale textured patterns may offer a more elegant solution to the problem. Scientists at GE Global Research have found that ice has a harder time sticking to surfaces that are superhydrophobic (very difficult to wet). Nanoscale structures that minimize the area that water will touch can also delay ice formation by reducing the rate of heat transfer and providing fewer possible nucleation sites for ice crystals to start growing. The researchers tested how likely ice was to form on a range of surfaces under conditions that mimicked real-world applications, such as an airplane wing smashing into water droplets at high speeds. They also tested how varying temperature and humidity affected the surfaces’ anti-icing properties. High humidity and extra low temperatures lessened the effectiveness of certain anti-icing textures, making it important to design tests across a range of conditions. Azar Alizadeh from GE Global Research will present results from a systematic study of early ice formation and offer perspective on the practical prospects of using textured surfaces for anti-icing applications.
Session B42.000132 – Development of nanostructured surfaces for ice protection applications
Making E-Readers and Other Electronics Out of Paper
If one of the main goals of electronic paper is to replicate the look and feel of actual ink on paper, then you might argue that paper is the ideal material to use for e-reader displays, say solid state electronics researchers from the University of Cincinnati in Ohio. Paper is a relatively inexpensive abundant, biodegradable and renewable resource. Using the principle of electrowetting, in which oil-based inks are made to move across a material using changes in voltage, hydrophobic paper could make a flexible substrate for an e-reader display. This design would also allow for colored displays that can change quickly enough to produce videos. The University of Cincinnati team, led by Andrew Steckl, has demonstrated that electrowetting works on paper substrates and that it is possible to obtain switching speeds similar to those on conventional glass backgrounds. Steckl will discuss recent breakthroughs in the use of paper for e-readers as well as other uses, such as in biochips, sensors, batteries, and circuits.
Session B42.00013 – Paper Inside? - New Thinking for Biochip and Other Applications
New Uniformly Strong Diamonds
Diamonds may be super hard, but they still have a weakness. Along certain directions, diamonds can be cleaved on planes of weakness, allowing jewelry manufacturers to cut diamonds. Now there’s a new form of carbon that is as strong as diamonds in all directions: the amorphous diamond. Researchers from Stanford University and the Carnegie Institute of Washington compressed glassy carbon to extreme pressures of over 400,000 times atmospheric pressure. Once pressurized, the carbon became as hard as a diamond, and maintained this hardness in every direction — unlike traditional diamonds. Amorphous diamonds lack the crystalline structure of natural diamonds, but they may have more practical applications. For instance, the team could use amorphous diamonds as high pressure anvils, enabling them to squeeze other objects tighter than ever before. Also, the team was able to tune the hardness of the diamond by applying various pressures. Experiments using this tunable diamond may unlock secrets about the high-pressure environment underneath the Earth’s surface.
Session V25.00006 – Amorphous diamond -- A high-pressure superhard carbon allotrope
Snakes on a Plane
Friction plays a major role in limbless locomotion. To measure this effect, researchers at the Georgia Institute of Technology experimentally tested a snake’s ability to change the amount of friction it generates in different directions. This amazing ability to actively control its coefficients of friction enables a snake to slither in a remarkably energy-efficient way. The researchers first measured the geometry and material properties of snake scales. They then conducted a series of friction measurements, testing the snake’s ability to hold on to different materials by placing it on a plane and then tilting it until the snake could no longer hold on and slid down the hill. To understand the importance of active control, the researchers conducted the studies using both conscious and unconscious snakes. They were surprised to observe that a conscious snake on Styrofoam has a frictional anisotropy – or the ratio of backward friction to forward friction – twice that of an unconscious snake. A conscious snake can contract its ventral (underbody) muscles in a controlled manner and also lift parts of its body in order to change the angle of attack of its ventral scales. As a result, the snake can increase its backward friction coefficient as well as its friction anisotropy and provide a better grip. This verifies that snakes can control their frictional properties while reducing the cost of their locomotion. Modeling performed in conjunction with the experiments suggests how scales may interact with the surface topography to generate anisotropic friction. A potential application of this research is the development of “smart scales” or “smart treads” that robots could use to reduce the cost of their locomotion.
Session W39.00011 – Snakeskin tribology: How snakes generate large frictional anisotropy
Google Database Reveals Evolution of Words
Major historical events and technological advances such as autocorrect have been changing how languages develop over time. Researchers at Boston University have analyzed more than 10 million words from Google’s publicly available Ngram database to see what determines the fate of new words. The team’s analysis suggests that words compete in a common environment for survival, and words consistently tend to become widely accepted if they can survive for about 40 years – the typical amount of time between first usage of a word and its introduction into dictionaries. In particular, the researchers found that words are more likely to undergo either rapid usage growth or quick death during global events such as World War I. The research also suggests that the proliferation of immediate spelling correction has reduced the amount of variations of certain words, leading to a more standardized language. Furthermore, Google’s database stretches back to 1800, which allowed the researchers to closely examine the revival of spoken Hebrew after centuries of dormancy. With this analysis, the team gained valuable insights into the development of a practically new spoken language being introduced to the world. This research is included in the J54 session on social networks, which will feature various other examinations on social media use, travel patterns and network modeling.
Session J54.00011 – The Growth Dynamics of Words: How Historical Context Shapes the Competitive Linguistic Environment
Session J54 – Focus Session: Complex and Co-evolving Networks - Empirical Studies of Social Networks
Pac-Man Molecule Tracks Chemical Reactions
By harnessing the Pac-Man-like chomping ability of lysozyme – a bacteria-munching enzyme found in humans – and latching it on to a carbon nanotube, researchers from the University of California, Irvine, have created the most precise chemical-reaction monitor ever developed. When lysozyme encounters particular molecules, either free-floating or part of the cell walls of bacteria , it rips into them with a rapid chomping motion, quickly breaking apart the molecules or damaging cell walls. Depending on the concentration and the precise make-up of the target molecules, the lysozyme reacts at different speeds. The nanotube sensor functions so efficiently because all of the motions and activity of the lysozyme get converted into an electric signal, recording the biochemical activity of the lysozyme. Further research reveals that deleting a single type of chemical bond from polysaccharide (a chemical that makes up bacterial cell walls), speeds up the action of the lysozyme by 50 percent, possibly providing new insights into the molecule’s bacteria-fighting abilities. The monitoring technique is part of a toolbox for understanding really complex molecules and their chemistry. It enables the researchers to quantify the effects of mutations, observe interference by pharmaceuticals, and measure the binding of molecules at docking sites. Future applications may include sensor or detector technologies, though its first practical application will be in laboratory use.
Session H7.00002 – The transduction mechanism of carbon nanotube transistors monitoring single molecule protein dynamics
Session W40.00010 – Comprehensive single molecule dynamics and functions of lysozyme upon linear and cross-linked substrate using a carbon nanotube circuit
A First Look at How Nanoparticles Move Around the Planet
Nanoparticles that occur naturally are everywhere; you literally take in thousands-to-millions of them with each breath. But though they are incalculably plentiful and ubiquitous, they are tremendously difficult to study because of their nanoscopic size (approximately ten thousand times narrower than a human hair). Michael Hochella of Virginia Tech in Blacksburg has developed the first estimates of the worldwide abundance and migration of these vanishingly small particles. His team also concluded that the largest natural producer of nanoparticles are the soils of the world’s continents. About 10 billion tons of mineral nanoparticles are eroded off the continents and deposited by rivers at the continental edges each year, with only two percent ending up in Earth’s oceans – matching the amount carried to the oceans by winds, icebergs, glaciers, and other means. These results provide valuable clues about how so-called engineered nanoparticles will move through the environment once they are released (intentionally or inadvertently). These estimates are environmentally important because certain materials that are benign or inert on the macroscale can take on new, reactive properties on the nanoscale. If they are harmful, we will have a better idea of how they will spread or stay put, depending on their chemical and physical properties.
Session P36.00001 – Nanominerals, Mineral Nanoparticles, and Earth Processes: Details on How Nanoparticles Work in the Environment
Containing Damage During a Financial Crisis
As global financial markets continue their slow recovery, the science of complex systems is being harnessed to find ways to contain the damage, should another financial meltdown be on the horizon. The key, according to Antonio Scala of Consiglio Navionale delle Ricerche in Italy and colleagues, is to enable greater disclosure of financial strength and to take active steps to immunize the institutions that have the greatest connectivity to the rest of the financial marketplace. The researchers developed their analysis by looking at the network of liaisons among financial institutions and ranking them based on their connectivity. This identifies the fraction of “ill” institutions that could trigger a crisis and make it propagate. The most important and most challenging aspect in making this model work is gathering data on these interconnections. Institutions would likely be hesitant to provide this information due to concerns about privacy, competition, and security. In their studies, the researchers looked for institutions that had the greatest ties to other institutions. Once these institutions have been identified and ranked, the key according to the researchers is to “immunize” them. This means that such institutions should not be disconnected, but rather be allowed to absorb the distress of the other financial institutions linked to them. How to attain such an immunization is a political matter and not linked to the model. The researchers also note that financial institutions often have multiple connections at multiple layers (the over-night market is very different from long-term borrowing). Future models will address these multi-layered complex systems, hopefully enabling more accurate immunizing recommendations during a financial crisis.
Session H54.00001 – Robustness and Assortativity for Diffusion-like Processes in Scale- free Networks
Improving the Safety of Soviet-Era Nuclear Reactors
VVER nuclear reactors, a kind of reactor designed and built by the Soviet Union, still provide electricity to customers throughout Eastern Europe and the former Soviet Republics. Demetra Papadopoulou of Neumann University in Pennsylvania will present an assessment of the consequences should a major accident occur at one of these reactors. She will give estimates of the number of cancer cases that could result from a level-7 accident, the highest level on the international nuclear event scale, and the same level assigned to the Chernobyl and Fukushima nuclear accidents. Such an accident would release large amounts of radioactive material that could spread over a wide area through air and ground contamination. The environmental damage could also destabilize new democratic governments and require expensive clean-up operations. VVER reactors may have safety deficiencies in the fire protection, reactor confinement, and emergency cooling systems. They may also have underdeveloped emergency procedures and training methods in place. Papadopoulou will discuss progress by organizations such as the International Atomic Energy Agency, the Organization for Economic Cooperation and Development, and the European Commission to improve safety at Soviet-designed reactors through collaboration with host countries.
Session L37.00006 – VVER Reactor Safety in Eastern Europe and Former Soviet Union
The Physics of Ponytails
From Judy Jetson to Cyndi Lauper, ponytails can be a stylish way to coif your tresses. Now a team of physicists in the United Kingdom has found a surprisingly simple mathematical description of the ponytail that allows scientists to predict its shape based on a few measureable characteristics of individual hairs. The team – comprising researchers from the University of Cambridge; the University of Warwick; and Unilever, a large multinational consumer goods company – measured the shapes of ponytails taken from commercially available hair samples, and tracked the geometry of individual hairs with the help of high-resolution stereoscopic imaging. Taking inspiration from a 1940s work that attempted to mathematically describe the compressibility of wool fibers, the team constructed what they call the ponytail shape equation, which has three main ingredients: the individual hairs’ elasticity, response to gravity, and intrinsic waviness or fluffiness. Besides contributing to an understanding of what they call the “enchanting problem” of ponytail shapes, the authors say that their remarkably simple equation may aid in understanding many types of fiber interactions. As a next step, the team will test their theory against a wider range of hair types, and might even take a swing at describing the physics of ponytails in action.
Session H52.00003 – The Shape of a Ponytail and the Statistical Physics of Hair Fiber Bundles
Uses for Real Spider Silk in Electronics
Spider silk is a readily available material – in Florida, at least. Engineers from Florida State University (FSU) in Tallahassee will discuss their work adapting real spider silk for a range of electronic devices, including heart pulse-monitoring sensors, electrical contacts for delicate single-crystal materials, and filaments for incandescent bulbs. Previous studies have mainly focused on the mechanical or biochemical properties of spider silk. In this work, the FSU team tried to push spider silk’s applications into the world of electrical measurements and devices. Using silks harvested from three types of spiders – the golden orb weaving spider, the southern house spider, and the vibrating spider, whose so-called lifeline silks are not sticky – researchers studied how the electrical conductivity of spider silk changes in response to several types of preparation, including pyrolization (the process of charring), humidity, doping with iodine, or coating with a thin layer of gold. The team found that the material’s conductivity can be increased by as much as 600 percent by iodine doping. Because spider silk is flexible and extremely thin, researchers found that a highly conductive and robust, gold-coated version could be used to make electrical contacts to objects that are small and delicate, such as those used in the fields of organic semiconductors and magnets. The researchers also fabricated carbon nanotube-coated spider silk that has enough strain sensitivity to detect a pulse near the wrist, and a pyrolized silk that could be used as the filament in an incandescent bulb. The authors hope their work will encourage geneticists and others to find more productive ways of producing synthetic spider silk, and will serve as a roadmap for future studies on the use of natural protein polymers in unconventional applications.
Session W49.00012 – Physical Characterization of Functionalized Silk Material for Electronic Application and Devices
More Spider Silk Studies
Studies of materials inspired by spider silk will be presented in several March meeting sessions. A team from Tufts University in Medford, Mass., will explain how they used synthetic materials inspired by spider silk to explore the origin of self-assembly behavior: researchers were able to control a synthetic silk-like copolymer’s ability to self-assemble by varying elements of the structure, such as the length of the molecules and the temperature at which the material was prepared. Materials scientists from the University of Akron in Ohio will discuss how the physical structure of spider silks at the nano, micro, and macro scales contributes to the silk’s adhesive properties. And mechanical engineers from the Ecole Polytechnique de Montreal in Quebec will show how to fabricate a tough new material inspired by spider silk: a thread of viscous solution, trickling like honey onto a table, buckles as it hits a surface, giving rise to coiling patterns with mechanical bonds that play an analogous role to the hydrogen bonds that give spider silk protein its toughness.
Session V50.00009 – Self-assembly Morphology and Crystallinity Control of Di-block Copolymer Inspired by Spider Silk
Session Y47.00010 – From Nano to Micro: Importance of Structure and Architecture in Spider Silk Adhesives
Session H52.00009 – Microfabrication of a spider-silk analogue through the liquid rope coiling instability
Reverse Evolution: Finding Conditions for Ancestral Regression
Natural selection ensures that the best-adapted organisms outcompete others in their environment. But sometimes organisms undergo reverse evolution, reverting back to their ancestral characteristics. Longzhi Tan and his colleagues at the Massachusetts Institute of Technology will describe how insights from bacterial DNA shed light on when and how animals exhibit reverse evolution. The peppered moths of Great Britain, for instance, were mostly white or light gray before the industrial revolution. Soot-stained trees eventually made the rarer black peppered moths more easily hidden, and their population flourished. After environmental controls were placed on industries, the soot leveled off, and the lighter colored moths became increasingly common. Tan and his colleagues have studied this phenomenon at the genetic level, showing that slow environmental changes in small populations lead to more cases of reverse evolution. Although reverse evolution is possible, the team found that larger populations are less likely to undergo this transition, and more complex adaptations are less likely to be reversed. With this new data, the researchers hope to better explain how animals, like the peppered moth, revert back to their once-dominant state after environmental changes.
Session B51.00008 – Hidden Randomness between Fitness Landscapes Limits Reverse Evolution
Dramatic advances in the understanding of elasticity, fluid flow, fracture, adhesion and other mechanical properties of various materials will be highlighted at the APS March Meeting with a collection of eight Extreme Mechanics focus sessions. The sessions include dozens of talks that provide new insight into subjects such as light-driven origami, the rapid motions of carnivorous plants, the influence of tidal motion on earthquakes, and much more.
Session H52: Extreme Mechanics – Rods
Session J52: Extreme Mechanics – Plates
Session L52: Extreme Mechanics – Origami, Creasing, and Folding
Session P52: Extreme Mechanics – Structures for Form and Function
Session Q52: Extreme Mechanics – Shells and Snapping
Session V52: Extreme Mechanics – Biological Systems and Structures
Session W52: Extreme Mechanics – Fluid-Structure Interactions and Swelling
Session X52: Extreme Mechanics – Fracture, Friction, and Frequencies