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  • richardmitnick 6:53 am on November 26, 2016 Permalink | Reply
    Tags: A distinct state of matter, , , Caltech, New Clues Emerge in 30-Year-Old Superconductor Mystery, Nonlinear optical rotational anisotropy, Pseudogap,   

    From Caltech: “New Clues Emerge in 30-Year-Old Superconductor Mystery” 

    Caltech Logo

    Caltech

    11/21/2016

    Whitney Clavin
    (626) 395-1856
    wclavin@caltech.edu

    1
    An artistic representation of the data showing the breaking of spatial inversion and rotational symmetries in the pseudogap region of superconducting materials—evidence that the pseudogap is a distinct phase of matter. Rings of light reflected from a superconductor reveal the broken symmetries. Credit: Hsieh Lab/Caltech

    One of the greatest mysteries of experimental physics is how so-called high-temperature superconducting materials work. Despite their name, high-temperature superconductors—materials that carry electrical current with no resistance—operate at chilly temperatures less than minus 135 degrees Celsius. They can be used to make superefficient power cables, medical MRIs, particle accelerators, and other devices. Cracking the mystery of how these materials work could lead to superconducting devices that operate at room temperatures—and could revolutionize electrical devices, including laptops and phones.

    In a new paper in the journal Nature Physics, researchers with the Institute for Quantum Information and Matter at Caltech have at last solved one piece of this enduring puzzle. They have confirmed that a transitional phase of matter called the pseudogap—one that occurs before these materials are cooled down to become superconducting—represents a distinct state of matter, with properties very different from those of the superconducting state itself.

    When matter transitions from one state, or phase, to another—say, water freezing into ice—there is a change in the ordering pattern of the materials’ particles. Physicists previously had detected hints of some type of ordering of electrons inside the pseudogap state. But exactly how they were ordering—and whether that ordering constituted a new state of matter—was unclear until now.

    “A peculiar property of all these high-temperature superconductors is that just before they enter the superconducting state, they invariably first enter the pseudogap state, whose origins are equally if not more mysterious than the superconducting state itself,” says David Hsieh, professor of physics at Caltech and principal investigator of the new research. “We have discovered that in the pseudogap state, electrons form a highly unusual pattern that breaks nearly all of the symmetries of space. This provides a very compelling clue to the actual origin of the pseudogap state and could lead to a new understanding of how high-temperature superconductors work.”

    The phenomenon of superconductivity was first discovered in 1911. When certain materials are chilled to super-cold temperatures, as low as a few degrees above absolute zero (a few degrees Kelvin), they carry electrical current with no resistance, so that no heat or energy is lost. In contrast, our laptops are not made of superconducting materials and therefore experience electrical resistance and heat up.

    Chilling materials to such extremely low temperatures requires liquid helium. However, because liquid helium is rare and expensive, physicists have been searching for materials that can function as superconductors at ever-higher temperatures. The so-called high-temperature superconductors, discovered in 1986, are now known to operate at temperatures up to 138 Kelvin (minus 135 degrees Celsius) and thus can be cooled with liquid nitrogen, which is more affordable than liquid helium. The question that has eluded physicists, however—despite three Nobel Prizes to date awarded in the field of superconductivity—is exactly how high-temperatures superconductors work.

    The dance of superconducting electrons

    Materials become superconducting when electrons overcome their natural repulsion and form pairs. This pairing can occur under extremely cold temperatures, allowing the electrons, and the electrical currents they carry, to move unencumbered. In conventional superconductors, electron pairing is caused by natural vibrations in the crystal lattice of the superconducting material, which act like glue to hold the pairs together.

    But in high-temperature superconductors, this form of “glue” is not strong enough to bind the electron pairs. Researchers think that the pseudogap, and how electrons order themselves in this phase, holds clues about what this glue may constitute for high-temperature superconductors. To study electron ordering in the pseudogap, Hsieh and his team have invented a new laser-based method called nonlinear optical rotational anisotropy. In the method, a laser is pointed at the superconducting material; in this case, crystals of ytttrium barium copper oxide (YBa2Cu3Oy). An analysis of the light reflected back at half the wavelength compared to that going in reveals any symmetry in the arrangement of the electrons in the crystals.

    Broken symmetries point to new phase

    Different phases of matter have distinct symmetries. For example, when water turns into ice, physicists say the symmetry has been “broken.”

    “In water,” Hsieh explains, “the H2O molecules are pretty randomly oriented. If you were swimming in an infinite pool of water, your surroundings look the same no matter where you are. In ice, on the other hand, the H2O molecules form a regular periodic network, so if you imagine yourself submerged in an infinite block of ice, your surroundings appear different depending on whether you are sitting on an H or O atom. Therefore, we say that the translational symmetry of space is broken in going from water to ice.”

    With the new tool, Hsieh’s team was able to show that the electrons cooled to the pseudogap phase broke a specific set of spatial symmetries called inversion and rotational symmetry. “As soon as the system entered the pseudogap region, either as a function of temperature or the amount of oxygen in the compound, there was a loss of inversion and rotational symmetries, clearly indicating a transition into a new phase of matter,” says Liuyan Zhao, a postdoctoral scholar in the Hsieh lab and lead author of the new study. “It is exciting that we are using a new technology to solve an old problem.”

    “The discovery of broken inversion and rotational symmetries in the pseudogap drastically narrows down the set of possibilities for how the electrons are self-organizing in this phase,” says Hsieh. “In some ways, this unusual phase may turn out to be the most interesting aspect of these superconducting materials.”

    The Nature Physics study, entitled A global-inversion-symmetry-broken phase inside the pseudogap region of YBa2Cu3Oy, was funded by the Army Research Office, the National Science Foundation, the Gordon and Betty Moore Foundation, the Canadian Institute for Advanced Research, and the Natural Sciences and Engineering Research Council. Other authors are C. A. Belvin of Wellesley College, Massachusetts; R. Liang, D.A. Bonn, and W.N. Hardy of the University of British Columbia, Vancouver; and N.P. Armitage of The Johns Hopkins University, Baltimore.

    See the full article here .

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    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”
    Caltech buildings

     
  • richardmitnick 7:52 am on November 5, 2016 Permalink | Reply
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    From Caltech: “Realistic Solar Corona Loops Simulated in Lab” 

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    Caltech

    11/04/2016

    Robert Perkins
    (626) 395-1862
    rperkins@caltech.edu

    1
    Side-by-side: A real coronal loop (left) compared to one simulated in Paul Bellan’s lab (right).
    Credit: Courtesy of P. Bellan/Caltech

    Caltech applied physicists have experimentally simulated the sun’s magnetic fields to create a realistic coronal loop in a lab.

    Coronal loops are arches of plasma that erupt from the surface of the sun following along magnetic field lines. Because plasma is an ionized gas—that is, a gas of free-flowing electrons and ions—it is an excellent conductor of electricity. As such, solar corona loops are guided and shaped by the sun’s magnetic field.

    The earth’s magnetic field acts as a shield that protects humans from the strong X-rays and energized particles emitted by the eruptions, but communications satellites orbit outside this shield field and therefore remain vulnerable. In March 1989, a particularly large flare unleashed a blast of charged particles that temporarily knocked out one of the National Oceanic and Atmospheric Administration’s geostationary operational environmental satellites that monitor the earth’s weather; caused a sensor problem on the space shuttle Discovery; and tripped circuit breakers on Hydro-Québec’s power grid, which blacked out the province of Quebec in Ontario, Canada, for nine hours.

    “This potential for causing havoc—which only increases the more humanity relies on satellites for communications, weather forecasting, and keeping track of resources—makes understanding how these solar events work critically important,” says Paul Bellan, professor of applied physics in the Division of Engineering and Applied Science.

    Although simulated coronal loops have been created in labs before, this latest attempt incorporated a magnetic strapping field that binds the loop to the sun’s surface. Think of a strapping field like the metal hoops on the outside of a wooden barrel. While the slats of the barrel are continually under pressure pushing outward, the metal hoops sit perpendicularly to the slats and hold the barrel together.

    The strength of this strapping field diminishes with distance from the sun. This means that when close to the solar surface, the loops are clamped down tightly by the strapping field but then can break loose and blast away if they rise to a certain altitude where the strapping field is weaker. These eruptions are known as solar flares and coronal mass ejections (CMEs).

    CMEs are rope-like discharges of hot plasma that accelerate away from the sun’s surface at speeds of more than a million miles per hour. These eruptions are capable of releasing energy equivalent to 1 billion megatons of TNT, making them potentially the most powerful explosions in the solar system. (CMEs are not to be confused with solar flares, which often occur as part of the same event. Solar flares are bursts of light and energy, while CMEs are blasts of particles embedded in a magnetic field.)

    The simulated loops and strapping fields provide new insight into how energy is stored in the solar corona and then released suddenly. Bellan worked with Caltech graduate student Bao Ha (MS ’10, PhD ’16) to create the strapping field and coronal loop. The results of their experiments were published in the journal Geophysical Research Letters on September 17, 2016.

    Bellan and his colleagues have been working on laboratory-scale simulations of solar corona phenomena for two decades. In the lab, the team generates ropes of plasma in a 1.5-meter-long vacuum chamber.

    “Studying coronal mass ejections is challenging, since humans do not know how and when the sun will erupt. But laboratory experiments permit the control of eruption parameters and enable the systematic explorations of eruption dynamics,” says Ha, lead author of the GRL paper. “While experiments with the same eruption parameters are easily reproducible, the loop dynamics vary depending on the configuration of the strapping magnetic field.”

    Simulating a strapping field with strength that fades over the relatively short length of the vacuum chamber proved difficult, Bellan says. In order to make it work, Ha and Bellan had to engineer electromagnetic coils that produce the strapping field inside the chamber itself.

    After more than three years of design, fabrication, and testing, Bellan and Ha were able to create a strapping field that peaks in strength about 10 centimeters away from where the plasma loop forms, then dies off a short distance farther down the vacuum chamber.

    The arrangement allows Bellan and Ha to watch the plasma loop slowly grow in size, then reach a critical point and fire off to the far end of the chamber.

    Next, Bellan plans to measure the magnetic field inside the erupting loop and also study the waves that are emitted when plasmas break apart.

    Their paper, titled Laboratory demonstration of slow rise to fast acceleration of arched magnetic flux ropes, is available online at http://onlinelibrary.wiley.com/doi/10.1002/2016GL069744/full. The research was supported by the National Science Foundation, the Air Force Office of Scientific Research, and the U.S. Department of Energy Office of Science, Office of Fusion Energy Sciences.

    See the full article here .

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    Caltech campus
    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”

     
  • richardmitnick 3:59 pm on October 19, 2016 Permalink | Reply
    Tags: Caltech, Curious Tilt of the Sun Traced to Undiscovered Planet,   

    From Caltech: “Curious Tilt of the Sun Traced to Undiscovered Planet” 

    Caltech Logo
    Caltech

    10/19/2016

    Robert Perkins
    (626) 395-1862
    rperkins@caltech.edu

    1
    This artistic rendering shows the distant view from Planet Nine back towards the sun. The planet is thought to be gaseous, similar to Uranus and Neptune. Hypothetical lightning lights up the night side. Credit: Caltech/R. Hurt (IPAC).

    Planet Nine—the undiscovered planet at the edge of the Solar System that was predicted by the work of Caltech’s Konstantin Batygin and Mike Brown in January 2016—appears to be responsible for the unusual tilt of the sun, according to a new study.

    The large and distant planet may be adding a wobble to the solar system, giving the appearance that the sun is tilted slightly.

    “Because Planet Nine is so massive and has an orbit tilted compared to the other planets, the solar system has no choice but to slowly twist out of alignment,” says Elizabeth Bailey, a graduate student at Caltech and lead author of a study announcing the discovery.

    All of the planets orbit in a flat plane with respect to the sun, roughly within a couple degrees of each other. That plane, however, rotates at a six-degree tilt with respect to the sun—giving the appearance that the sun itself is cocked off at an angle. Until now, no one had found a compelling explanation to produce such an effect. “It’s such a deep-rooted mystery and so difficult to explain that people just don’t talk about it,” says Brown, the Richard and Barbara Rosenberg Professor of Planetary Astronomy.

    Brown and Batygin’s discovery of evidence that the sun is orbited by an as-yet-unseen planet—that is about 10 times the size of Earth with an orbit that is about 20 times farther from the sun on average than Neptune’s—changes the physics. Planet Nine, based on their calculations, appears to orbit at about 30 degrees off from the other planets’ orbital plane—in the process, influencing the orbit of a large population of objects in the Kuiper Belt, which is how Brown and Batygin came to suspect a planet existed there in the first place.

    “It continues to amaze us; every time we look carefully we continue to find that Planet Nine explains something about the solar system that had long been a mystery,” says Batygin, an assistant professor of planetary science.

    Their findings have been accepted for publication in an upcoming issue of the Astrophysical Journal, and will be presented on October 18 at the American Astronomical Society’s Division for Planetary Sciences annual meeting, held in Pasadena.

    The tilt of the solar system’s orbital plane has long befuddled astronomers because of the way the planets formed: as a spinning cloud slowly collapsing first into a disk and then into objects orbiting a central star.

    Planet Nine’s angular momentum is having an outsized impact on the solar system based on its location and size. A planet’s angular momentum equals the mass of an object multiplied by its distance from the sun, and corresponds with the force that the planet exerts on the overall system’s spin. Because the other planets in the solar system all exist along a flat plane, their angular momentum works to keep the whole disk spinning smoothly.

    Planet Nine’s unusual orbit, however, adds a multi-billion-year wobble to that system. Mathematically, given the hypothesized size and distance of Planet Nine, a six-degree tilt fits perfectly, Brown says.

    The next question, then, is how did Planet Nine achieve its unusual orbit? Though that remains to be determined, Batygin suggests that the planet may have been ejected from the neighborhood of the gas giants by Jupiter, or perhaps may have been influenced by the gravitational pull of other stellar bodies in the solar system’s extreme past.

    For now, Brown and Batygin continue to work with colleagues throughout the world to search the night sky for signs of Planet Nine along the path they predicted in January. That search, Brown says, may take three years or more.

    See the full article here .

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    Caltech campus
    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”

     
  • richardmitnick 7:38 am on October 15, 2016 Permalink | Reply
    Tags: , , Caltech, , , Mike Brown   

    From Caltech Astronomer Mike Brown: “How many dwarf planets are there in the outer solar system? (updates daily)” 

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    Caltech

    1

    Mike Brown

    How many dwarf planets are there in the outer solar system? (updates daily)
    (As of 1 Nov 2013 also includes latest thermal and occultation results)
    As of Sat Oct 15 2016
    there are:
    10 objects which are nearly certainly dwarf planets,
    30 objects which are highly likely to be dwarf planets,
    75 objects which are likely to be dwarf planets,
    147 objects which are probably dwarf planets, and
    695 objects which are possibly dwarf planets.

    In 2006, when the vote on the definition of “planet” was made, and the eight dominant bodies in the solar system were declared (quite rationally) a class separate from the others, a new class of objects was defined. The “dwarf planets” are all of those objects which are not one of the eight dominant bodies (Mercury through Neptune) yet still, at least in one way, resemble a planet. In other words, a dwarf planet is something that looks like a planet, but is not a planet. Specifically this means that dwarf planets are bodies in the solar system which are large enough to become round due to their own gravitational attraction.

    Why do astronomers care about round? If you place a boulder in space it will just stay whatever irregular shape it is. If you add more boulders to it you can still have an irregular pile. But if you add enough boulders to the pile they will eventually pull themselves into a round shape. This transition from irregularly shaped to round objects is important in the solar system, and, in some ways, marks the transition from an object without and with interesting geological and planetary processes occuring (there are many many other transitions that are equally important, however, a fact that tends to be overlooked in these discussions).

    How many dwarf planets are there? Ceres is the only asteroid that is known to be round.

    2
    Ceres

    After that it gets complicated. All of the rest of the new dwarf planets are in the distant region of the Kuiper belt, where we can’t actually see them well enough to know for sure if they are round or not.

    Kuiper Belt. Minor Planet Center
    Kuiper Belt. Minor Planet Center

    While we can’t see most of the objects in the Kuiper belt well enough to determine whether they are round or not, we can estimate how big an object has to be before it becomes round and therefore how many objects in the Kuiper belt are likely round. In the asteroid belt Ceres, with a diameter of 900 km, is the only object large enough to be round, so somewhere around 900 km is a good cutoff for rocky bodies like asteroids. Most Kuiper belt objects have a lot of ice in their interiors, though. Ice is not as hard as rock, so it less easily withstands the force of gravity, and it takes less force to make an ice ball round. The best estimate for how big an icy body needs to be to become round comes from looking at icy satellites of the giant planets. The smallest body that is generally round is Saturn’s satellite Mimas, which has a diameter of about 400 km.

    4
    Mimas

    Several satellites which have diameters around 200 km are not round. So somewhere between 200 and 400 km an icy body becomes round. Objects with more ice will become round at smaller sizes while those with less rock might be bigger. We will take 400 km as a reasonable lower limit and assume that anything larger than 400 km in the Kuiper belt is round, and thus a dwarf planet.

    How many objects do we know in the Kuiper belt that are 400 km or larger? That question is harder to answer, because we don’t actually know how big most of the objects in the Kuiper belt are. While we can see how bright there are, we don’t know if they are bright because they are larger or are highly reflective. In the past, we had to just throw our hands up in the air and say we don’t know enough to even make reasonable guesses. But in the past few years, systematic measurements of the sizes of objects from the Spitzer Space Telescope and now the Herschel Space Telescope have taught us enought that we can make some reasonable estimates of how reflective objects are.

    NASA/Spitzer Telescope
    NASA/Spitzer Telescope

    ESA/Herschel
    ESA/Herschel

    (It’s complicated: read the details here ) These reasonable estimates, combined with all available actually measurements, give us the list of the largest Kuiper belt objects, sorted by diameter, below. Carefully note the lack of any error bars. Every single measurement or estimate below is uncertain to some extent or another. I don’t include the individual uncertainties in the table, but instead use the ensemble uncertainties to inform classification below. In other words: take the sizes of specific objects with bigger or smaller grains of salt.

    See the full article here .

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    Caltech campus
    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”

     
  • richardmitnick 5:10 pm on October 7, 2016 Permalink | Reply
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    From Caltech via phys.org: “California earthquakes discovered much deeper than originally believed” 

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    Caltech

    phys.org

    phys.org

    October 7, 2016
    Rong-Gong Lin Ii, Los Angeles Times

    1
    Seismogram being recorded by a seismograph at the Weston Observatory in Massachusetts, USA. Credit: Wikipedia

    Scientists in California have found that earthquakes can occur much deeper below the Earth’s surface than originally believed, a discovery that alters their understanding of seismic behavior and potential risks.

    Seismologists have long believed that earthquakes occur less than 12 to 15 miles underground. But the new research found evidence of quakes deeper than 15 miles, below the Earth’s crust and in the mantle.

    Three scientists at the California Institute of Technology in Pasadena studied data from state-of-the-art sensors installed in Long Beach atop the Newport-Inglewood fault, one of the most dangerous in the Los Angeles Basin and which caused the magnitude 6.4 Long Beach earthquake of 1933.

    After analyzing the data collected over six months by 5,000 sensors, scientists found quakes were occurring deep into the upper mantle, an area where the rock is so hot that it is no longer brittle like it is at the surface, but creeps, moving around like an extremely hard honey.

    It appeared that the Newport-Inglewood fault extended even into the mantle – past the uppermost layer of the Earth, the crust, where earthquakes long have been observed. Until now, researchers didn’t think earthquakes were possible there, said Caltech seismology professor Jean Paul Ampuero, one of three authors of the study, published Thursday in the journal Science.

    Ampuero said the research raised the possibility that the Newport-Inglewood and others, like the San Andreas, could see even more powerful earthquakes than expected. The earthquakes he and his colleagues studied were so deep that they were not felt at the surface by conventional seismic sensors.

    The new study [Science] indicates that a quake much closer to the surface could travel much deeper into the Earth, producing a stronger, more damaging, rupture than previously believed was possible.

    “That got us thinking – that if earthquakes want to get big, one way of achieving that is by penetrating deep,” Ampuero said. “The big question is: If the next, larger earthquake happens, if it manages to penetrate deeper than we think, it may be bigger than we expect.”

    It’s an idea that was first raised in 2012, also by Ampuero and several colleagues in the journal Science, when a magnitude 8.6 earthquake struck the Indian Ocean.

    That was the largest quake of its kind “that has ever happened,” Ampuero said. It happened on a fault known as a “strike-slip,” the same kind of fault as Newport-Inglewood and California’s mighty San Andreas, the state’s longest fault.

    But that Indian Ocean earthquake was so large, it was impossible to explain how it happened with existing science.

    So answering the question of how an 8.6 earthquake occurred required a new explanation – that perhaps the quake centered on a fault that not only ruptured the crust, but went deeper into the mantle.

    If deep earthquakes can occur on the Newport-Inglewood fault, then it’s possible Southern Californians could see earthquakes along this fault at an even greater magnitude than what is projected. According to Caltech, the probable magnitude of a large quake on the Newport-Inglewood fault ranges from 6.0 to 7.4.

    But there’s a lot more study that needs to be done.

    The deep quakes Caltech scientists detected were only microquakes – topping out at about a magnitude 2.

    Therefore, one alternate – and more comforting – possibility is that these deep earthquakes remain small and don’t help a large earthquake become stronger. With this theory, earthquakes in this deep zone occur in small pockets far away from each other and don’t link in a way that forces a big earthquake to get stronger.

    “This could be good news, in a way, because if they never break together, that means they can break in tiny earthquakes, but they cannot break in large ones,” Ampuero said. “So several questions are still open. I wouldn’t say that this is cause for alarm at this point. These are very interesting questions that we need to pursue.”

    Another thing to consider: The deep earthquakes were found in a 9-square-mile area underneath Long Beach, recorded over six months. When researchers looked farther northwest – over a shorter time period, only four weeks – they did not find deep earthquakes there.

    So it’s possible that deep earthquakes don’t exist everywhere on the Newport-Inglewood fault. But it’s also possible that scientists didn’t record any, and could catch some if they continue monitoring the area for a longer period.

    There’s a possibility that Long Beach is simply peculiar, and what’s found there isn’t found elsewhere. In Long Beach, scientists found evidence that there are some liquids flowing from the mantle up to the surface – an observation that was not found in another location on the Newport-Inglewood fault.

    The scientists obtained the data from a group who installed sensors to better understand the oil fields of the area. Once they collected it, the scientists had to design a program to process the massive amounts of data collected to understand what was going on miles underground, and invisible to conventional seismic sensing equipment.

    In addition to Ampuero, the other authors of the study are Asaf Inbal and Robert Clayton.

    See the full article here .

    QCN bloc

    Quake-Catcher Network

    The Quake-Catcher Network is a collaborative initiative for developing the world’s largest, low-cost strong-motion seismic network by utilizing sensors in and attached to internet-connected computers. With your help, the Quake-Catcher Network can provide better understanding of earthquakes, give early warning to schools, emergency response systems, and others. The Quake-Catcher Network also provides educational software designed to help teach about earthquakes and earthquake hazards.

    After almost eight years at Stanford, and a year at CalTech, the QCN project is moving to the University of Southern California Dept. of Earth Sciences. QCN will be sponsored by the Incorporated Research Institutions for Seismology (IRIS) and the Southern California Earthquake Center (SCEC).

    The Quake-Catcher Network is a distributed computing network that links volunteer hosted computers into a real-time motion sensing network. QCN is one of many scientific computing projects that runs on the world-renowned distributed computing platform Berkeley Open Infrastructure for Network Computing (BOINC).

    BOINCLarge

    BOINC WallPaper

    The volunteer computers monitor vibrational sensors called MEMS accelerometers, and digitally transmit “triggers” to QCN’s servers whenever strong new motions are observed. QCN’s servers sift through these signals, and determine which ones represent earthquakes, and which ones represent cultural noise (like doors slamming, or trucks driving by).

    There are two categories of sensors used by QCN: 1) internal mobile device sensors, and 2) external USB sensors.

    Mobile Devices: MEMS sensors are often included in laptops, games, cell phones, and other electronic devices for hardware protection, navigation, and game control. When these devices are still and connected to QCN, QCN software monitors the internal accelerometer for strong new shaking. Unfortunately, these devices are rarely secured to the floor, so they may bounce around when a large earthquake occurs. While this is less than ideal for characterizing the regional ground shaking, many such sensors can still provide useful information about earthquake locations and magnitudes.

    USB Sensors: MEMS sensors can be mounted to the floor and connected to a desktop computer via a USB cable. These sensors have several advantages over mobile device sensors. 1) By mounting them to the floor, they measure more reliable shaking than mobile devices. 2) These sensors typically have lower noise and better resolution of 3D motion. 3) Desktops are often left on and do not move. 4) The USB sensor is physically removed from the game, phone, or laptop, so human interaction with the device doesn’t reduce the sensors’ performance. 5) USB sensors can be aligned to North, so we know what direction the horizontal “X” and “Y” axes correspond to.

    If you are a science teacher at a K-12 school, please apply for a free USB sensor and accompanying QCN software. QCN has been able to purchase sensors to donate to schools in need. If you are interested in donating to the program or requesting a sensor, click here.

    BOINC is a leader in the field(s) of Distributed Computing, Grid Computing and Citizen Cyberscience.BOINC is more properly the Berkeley Open Infrastructure for Network Computing, developed at UC Berkeley.

    Earthquake safety is a responsibility shared by billions worldwide. The Quake-Catcher Network (QCN) provides software so that individuals can join together to improve earthquake monitoring, earthquake awareness, and the science of earthquakes. The Quake-Catcher Network (QCN) links existing networked laptops and desktops in hopes to form the worlds largest strong-motion seismic network.

    Below, the QCN Quake Catcher Network map
    QCN Quake Catcher Network map

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    About Phys.org in 100 Words

    Phys.org™ (formerly Physorg.com) is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004, Phys.org’s readership has grown steadily to include 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page.

    Caltech campus

    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”

     
  • richardmitnick 3:16 pm on September 28, 2016 Permalink | Reply
    Tags: , , Caltech, Modular Space Telescope Could Be Assembled By Robot,   

    From Caltech: “Modular Space Telescope Could Be Assembled By Robot” 

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    Caltech

    09/28/2016
    Robert Perkins
    (626) 395-1862
    rperkins@caltech.edu

    1
    Illustration shows how a robot could assemble the trusses that would support a massive telescope mirror. Credit: Sergio Pellegrino/Caltech

    2
    Figure shows how foldable truss modules can be combined and assembled to support stackable mirror modules, ultimately creating a single large mirror.
    Credit: Sergio Pellegrino/Caltech

    Seeing deep into space requires large telescopes. The larger the telescope, the more light it collects, and the sharper the image it provides.

    For example, NASA’s Kepler space observatory, with a mirror diameter of under one meter, is searching for exoplanets orbiting stars up to 3,000 light-years away. By contrast, the Hubble Space Telescope, with a 2.4-meter mirror, has studied stars more than 10 billion light-years away.

    Now Caltech’s Sergio Pellegrino and colleagues are proposing a space observatory that would have a primary mirror with a diameter of 100 meters—40 times larger than Hubble’s. Space telescopes, which provide some of the clearest images of the universe, are typically limited in size due to the difficulty and expense of sending large items into space. Pellegrino’s team would circumvent that issue by shipping the mirror up as separate components that would be assembled, in space, by robots.

    Their design calls for the use of more than 300 deployable truss modules that could be unfolded to form a scaffolding upon which a commensurate number of small mirror plates could be placed to create a large segmented mirror. The assembly of the scaffolding and the attachment of the many mirrors is a task well-suited to robots, Pellegrino and his colleagues say.

    In their concept, a spider-like, six-armed “hexbot” would assemble the trusswork and then crawl across the structure to build the mirror atop it. It was modeled on the JPL RoboSimian system, which in 2015 completed the DARPA Robotics Challenge, a federal competition aimed at spurring the development of robots that could perform complicated tasks that would be dangerous for humans. The hexbot would run on electrical power from the telescope’s solar grid. It would use four of its arms to walk—with one leg moving at any given time, while the three others remain securely attached to the structure. The two remaining arms would be free to assemble the trusses and mirrors.

    The team opted to pursue an ambitious 100-meter design. “We wanted to study how different kinds of architectures perform as the diameter is increased,” says Pellegrino, Joyce and Kent Kresa Professor of Aeronautics and Professor of Civil Engineering in Caltech’s Division of Engineering and Applied Science, and Jet Propulsion Laboratory Senior Research Scientist. “We found that far away from the Earth, a structurally connected telescope is much heavier than an architecture based on separate spacecraft for the primary mirror, the optics, and the instrumentation.”

    The realization of such an assembly is still decades away. However, Pellegrino and his colleagues are already working on the various technologies that will be needed to make it possible.

    The entire space observatory would be composed of the fully assembled mirror-and-truss structure and three other parts, flying in formation. An optics and instrumentation unit would be located about 400 meters from the mirror; a control unit, stationed about 400 meters beyond that, would align the system and keep it working properly; and a thin shade, roughly 20 meters in diameter, would shield the mirror from the sun to keep its temperature stable and consistent across its diameter.

    The four-part assembly would be stationed at one of the sun–earth Lagrange points—locations between the sun and the earth where the pull of gravity from two bodies locks a satellite into orbit with them, allowing it to maintain a stable position. There, the space observatory could peer deep into space without drifting out of place.

    Pellegrino collaborated with Joel Burdick, Nicolas Lee, and Kristina Hogstrom of Caltech, as well as Paul Backes, Christine Fuller, Brett Kennedy, Junggon Kim, Rudranarayan Mukherjee, Carl Seubert, and Yen-Hung Wu of JPL. A paper about the work, titled “Architecture for in-space robotic assembly of a modular space telescope,” was published by the Journal of Astronomical Telescopes, Instruments, and Systems. This research was supported by NASA and the W. M. Keck Institute for Space Studies.

    See the full article here .

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    Caltech campus
    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”

     
  • richardmitnick 1:46 pm on September 7, 2016 Permalink | Reply
    Tags: , , Caltech, Milky Way simulations   

    From Caltech: “Recreating Our Galaxy in a Supercomputer” 

    Caltech Logo

    Caltech

    09/07/2016
    Whitney Clavin
    (626) 395-1856
    wclavin@caltech.edu

    1
    Simulated view of our Milky Way galaxy, seen from a nearly face-on angle. This image was created by simulating the formation of our galaxy using a supercomputer, which, in this case, consisted of 2,000 computers linked together. Credit: Hopkins Research Group/Caltech

    2
    In a new simulation of the formation of our Milky Way galaxy, astronomers were able to, for the first time, correctly predict the number of dwarf galaxies observed today. Dwarf galaxies are small galaxies that swarm around the outside of the Milky Way. Prior simulations found thousands of them—far more than the 30 or so observed so far. This image from the new simulation shows our galaxy with the correct number of dwarf galaxies. The streak is a tidal tail from a torn-apart dwarf galaxy. Credit: Hopkins Research Group/Caltech

    Milky Way NASA/JPL-Caltech /ESO R. Hurt
    Milky Way NASA/JPL-Caltech /ESO R. Hurt

    Astronomers have created the most detailed computer simulation to date of our Milky Way galaxy’s formation, from its inception billions of years ago as a loose assemblage of matter to its present-day state as a massive, spiral disk of stars.

    The simulation solves a decades-old mystery surrounding the tiny galaxies that swarm around the outside of our much larger Milky Way. Previous simulations predicted that thousands of these satellite, or dwarf, galaxies should exist. However, only about 30 of the small galaxies have ever been observed. Astronomers have been tinkering with the simulations, trying to understand this “missing satellites” problem to no avail.

    Now, with the new simulation—which used a network of thousands of computers running in parallel for 700,000 central processing unit (CPU) hours—Caltech astronomers have created a galaxy that looks like the one we live in today, with the correct, smaller number of dwarf galaxies.

    “That was the aha moment, when I saw that the simulation can finally produce a population of dwarf galaxies like the ones we observe around the Milky Way,” says Andrew Wetzel, postdoctoral fellow at Caltech and Carnegie Observatories in Pasadena, and lead author of a paper about the new research, published August 20 in Astrophysical Journal Letters.

    One of the main updates to the new simulation relates to how supernovae, explosions of massive stars, affect their surrounding environments. In particular, the simulation incorporated detailed formulas that describe the dramatic effects that winds from these explosions can have on star-forming material and dwarf galaxies. These winds, which reach speeds up to thousands of kilometers per second, “can blow gas and stars out of a small galaxy,” says Wetzel.

    Indeed, the new simulation showed the winds can blow apart young dwarf galaxies, preventing them from reaching maturity. Previous simulations that were producing thousands of dwarf galaxies weren’t taking the full effects of supernovae into account.

    “We had thought before that perhaps our understanding of dark matter was incorrect in these simulations, but these new results show we don’t have to tinker with dark matter,” says Wetzel. “When we more precisely model supernovae, we get the right answer.”

    Astronomers simulate our galaxy to understand how the Milky Way, and our solar system within it, came to be. To do this, the researchers tell a computer what our universe was like in the early cosmos. They write complex codes for the basic laws of physics and describe the ingredients of the universe, including everyday matter like hydrogen gas as well as dark matter, which, while invisible, exerts gravitational tugs on other matter. The computers then go to work, playing out all the possible interactions between particles, gas, and stars over billions of years.

    “In a galaxy, you have 100 billion stars, all pulling on each other, not to mention other components we don’t see like dark matter,” says Caltech’s Phil Hopkins, associate professor of theoretical astrophysics and principal scientist for the new research. “To simulate this, we give a supercomputer equations describing those interactions and then let it crank through those equations repeatedly and see what comes out at the end.”

    The researchers are not done simulating our Milky Way. They plan to use even more computing time, up to 20 million CPU hours, in their next rounds. This should lead to predictions about the very faintest and smallest of dwarf galaxies yet to be discovered. Not a lot of these faint galaxies are expected to exist, but the more advanced simulations should be able to predict how many are left to find.

    The study, titled “Reconciling Dwarf Galaxies with ΛCDM Cosmology: Simulating A Realistic Population of Satellites Around a Milky Way-Mass Galaxy,” was funded by Caltech, a Sloan Research Fellowship, the National Science Foundation, NASA, an Einstein Postdoctoral Fellowship, the Space Telescope Science Institute, UC San Diego, and the Simons Foundation. Other coauthors on the study are: Ji-Hoon Kim of Stanford University, Claude-André Faucher-Giguére of Northwestern University, Dušan Kereš of UC San Diego, and Eliot Quataert of UC Berkeley.

    Carnegie Observatories Release

    See the full article here .

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    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”
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  • richardmitnick 7:36 am on September 7, 2016 Permalink | Reply
    Tags: , Caltech, Optical Solitons,   

    From Caltech: “New Breed of Optical Soliton Wave Discovered” 

    Caltech Logo

    Caltech

    09/06/2016

    Robert Perkins
    (626) 395-1862
    rperkins@caltech.edu

    1
    These optical microcavities are where solitons are created. The solitary waves circle around the microscopic disks at the speed of light.
    Credit: Qi-Fan Yang/Caltech

    Applied scientists led by Caltech’s Kerry Vahala have discovered a new type of optical soliton wave that travels in the wake of other soliton waves, hitching a ride on and feeding off of the energy of the other wave.

    Solitons are localized waves that act like particles: as they travel across space, they hold their shape and form rather than dispersing as other waves do. They were first discovered in 1834 when Scottish engineer John Scott Russell noted an unusual wave that formed after the sudden stop of a barge in the Union Canal that runs between Falkirk and Edinburgh. Russell tracked the resulting wave for one or two miles, and noted that it preserved its shape as it traveled, until he ultimately lost sight of it.

    He dubbed his discovery a “wave of translation.” By the end of the century, the phenomenon had been described mathematically, ultimately giving birth to the concept of the soliton wave. Under normal conditions, waves tend to dissipate as they travel through space. Toss a stone into a pond, and the ripples will slowly die down as they spread out away from the point of impact. Solitons, on the other hand, do not.

    In addition to water waves, solitons can occur as light waves. Vahala’s team studies light solitons by having them recirculate indefinitely in micrometer-scale circular circuits called optical microcavities. Solitons have applications in the creation of highly accurate optical clocks, and can be used in microwave oscillators that are used for navigation and radar systems, among other things.

    But despite decades of study, a soliton has never been observed behaving in a dependent—almost parasitic—manner.

    “This new soliton rides along with another soliton—essentially, in the other soliton’s wake. It also syphons energy off of the other soliton so that it is self-sustaining. It can eventually grow larger than its host,” says Vahala, Ted and Ginger Jenkins Professor of Information Science and Technology and Applied Physics and executive officer for applied physics and materials science in the Division of Engineering and Applied Science.

    Vahala likens these newly discovered solitons to pilot fish, carnivorous tropical fish that swim next to a shark so they can pick up scraps from the shark’s meals. And by swimming in the shark’s wake, the pilot fish reduce the drag of water on their own body, so they can travel with less effort.

    Vahala is the corresponding author of a paper in the journal Nature Physics announcing and describing the new type of soliton, dubbed the “Stokes soliton.” (The name “Stokes” was chosen for technical reasons having to do with how the soliton syphons energy from the host.) The new soliton was first observed by Caltech graduate students Qi-Fan Yang and Xu Yi. Because of the soliton’s ability to closely match the position and shape of the original soliton, Yang’s and Yi’s initial reaction to the wave was to suspect that laboratory instrumentation was malfunctioning.

    “We confirmed that the signal was not an artifact of the instrumentation by observing the signal on two spectrometers. We then knew it was real and had to figure out why a new soliton would spontaneously appear like this,” Yang says.

    The microcavities that Vahala and his team use include a laser input that provides the solitons with energy. This energy cannot be directly absorbed by the Stokes soliton—the “pilot fish.” Instead, the energy is consumed by the “shark” soliton. But then, Vahala and his team found, the energy is pulled away by the pilot fish soliton, which grows in size while the other soliton shrinks.

    “Once we understood the environment required to sustain the new soliton, it actually became possible to design the microcavities to guarantee their formation and even their properties like wavelength—effectively, color,” Yi says. Yi and Yang collaborated with graduate student Ki Youl Yang on the research.

    The research was funded by the Defense Advanced Research Projects Agency under the PULSE Program; NASA; the Kavli Nanoscience Institute; and the Institute for Quantum Information and Matter, a National Science Foundation Physics Frontiers Center supported by the Gordon and Betty Moore Foundation.

    See the full article here .

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    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”
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  • richardmitnick 7:21 am on September 2, 2016 Permalink | Reply
    Tags: , Caltech, , ,   

    From Caltech: Women in STEM – “Multitasking Protein Keeps Immune System Healthy” Beth Stadtmueller 

    Caltech Logo

    Caltech

    09/01/2016
    Lori Dajose

    1
    Simplified diagram of pIgR binding to an antibody. A) pIgR and an antibody. B) Recognition binding. pIgR chemically recognizes an antibody. C) Conformational change. The pIgR protein opens up. D) The bound state of pIgR and an antibody. Credit: B. Stadtmueller

    2
    Schematic summary highlighting the differences in pIgR structure among fish, birds and humans.
    Credit: B. Stadtmueller

    The polymeric immunoglobulin receptor, or pIgR, is a multitasking protein produced in the lining of mucosal surfaces, such as the intestines. It plays a pivotal role in the body’s immune functions by sequestering bacteria and by assisting antibodies—large proteins that can identify and neutralize specific bacteria and viruses. Now, scientists at Caltech have determined the three-dimensional structure of pIgR, providing important insights into how the protein keeps the immune system running smoothly.

    Beth Stadtmueller, a postdoctoral scholar in the laboratory of Centennial Professor of Biology Pamela Björkman, is the first author on two recent papers describing the findings.

    2
    Beth Stadtmueller

    “Proteins such as pIgR are folded into complicated shapes,” says Stadtmueller. “Having a complete model of a protein is analogous to an architectural model of a building showing scaled dimensions of walls, the locations of windows and doors, angles of the roof, and so on. Understanding the structure of this protein provides information on how it carries out normal functions while also providing a basis to rationally engineer modified proteins with enhanced functions, which could be used as therapeutics.”

    The pIgR protein is best known for attaching to antibodies and ferrying them from the bloodstream to the interior of the intestines, where the antibodies can neutralize pathogens. In mammals such as humans, the group discovered that pIgR looks like five round beads—biologists call these regions “domains”—that are connected to form a tightly closed, triangle-shaped loop. The group also showed that upon encountering an antibody, the pIgR molecule opens up—like changing from a fist to an open hand—to enclose around the antibody and to transport it into the intestines.

    While pIgR is crucial for helping antibodies to function, the protein also has disease-fighting abilities of its own. For example, some molecules of pIgR are released into the intestines where they alone engage bacteria, such as pneumonia-causing Streptococcus pneumoniae.

    The group also studied the structures of pIgR from fish and birds, to see how the protein has changed as vertebrates evolved. In fish, pIgR has only two domains and forms a straight line. In birds, an evolutionary intermediary between fish and humans, the protein has four domains. The group was surprised to find that the shape of the bird pIgR is not fixed in a closed loop or a straight line—it can change freely between closed and open configurations, and can grasp antibodies much like the human protein.

    “The human pIgR is like a door that has to be unlocked to open, whereas the bird pIgR is constantly opening and closing like a revolving door,” Stadtmueller says. “These are very different structures, which are likely to support functions unique to each protein.”

    “The immune system has changed considerably as vertebrates have evolved,” she adds. “Studying pIgR in a spectrum of vertebrates illustrates how the protein architecture has changed to support species-specific defense systems. It helps us to understand why certain immune system functions have evolved and provides a foundation to test their contributions to specific states of health and disease.”

    The three-dimensional structure of human pIgR is described in a March 2016 paper published in the journal eLife, titled The structure and dynamics of secretory component and its interactions with polymeric immunoglobulins. A follow-up study, titled Biophysical and biochemical characterization of avian secretory component provides structural insights into the evolution of the polymeric Ig receptor, describing the structure of avian pIgR, was published in the Journal of Immunology on August 15, 2016. The work was done in collaboration with the Hubbell laboratory at UCLA and supported by grants from the National Institute of Allergy and Infectious Diseases, the Cancer Research Irving Postdoctoral Fellowship, the Jules Stein Professorship Endowment, and the National Institutes of Health.

    See the full article here .

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    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”
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  • richardmitnick 4:00 pm on August 12, 2016 Permalink | Reply
    Tags: , Caltech, Mechanical chains made of soft matter that can transmit signals across long distances,   

    From Caltech: “The Utility of Instability” 

    Caltech Logo

    Caltech

    08/08/2016
    Robert Perkins
    (626) 395-1862
    rperkins@caltech.edu

    1
    A 3-D–printed logic gate with bistable elements linked together by springs to transmit signals. Credit: Dennis Kochmann/Caltech

    A team of researchers from Caltech and Harvard has designed and created mechanical chains made of soft matter that can transmit signals across long distances. Because they are flexible, the circuits could be used in machines such as soft robots or lightweight aircraft constructed from pliable, nonmetallic materials.

    Unlike hard materials, which transit signals readily, soft materials tend to absorb energy as it passes through them. An analogy is hitting a firm punching bag versus a soft one: with the firm bag, the energy of your punch moves through the bag and sends it swinging, but the soft bag deforms your fist like a lump of dough and therefore will swing less.

    To overcome that response, Caltech’s Dennis Kochmann, Chiara Daraio, and their colleagues created an unstable, “nonlinear” system. Their findings have appeared in three papers published over the past few months.

    “Engineers tend to shy away from instability. Instead, we take advantage of it,” says Kochmann, assistant professor of aerospace in the Division of Engineering and Applied Sciences, and one of the lead researchers on the project.

    Stable, or “linear,” systems are attractive to engineers because they are easy to model and predict. Take, for example, a spring: If you push on a spring, it will respond by pushing back with a force that is linearly proportional to how much force you apply. The response of a nonlinear system to that same push, by comparison, is not proportional, and can include sudden changes in the direction or amplitude of the responsive force.

    The nonlinear systems that Kochmann and his colleagues designed rely on bistable elements, or elements that can be stable in two distinct states. The bistable elements that the team developed consist of arches of an elastic material, each a few millimeters in size. The elements can be in either a convex or a concave position—and are stable in either configuration. However, if you push on the element in its convex position, it responds by pushing back against the direction of force until it snaps into a concave position, accompanied by a sudden release of energy in the opposite direction.

    “It’s an elastic response, and then a snap-through,” explains Daraio, professor of aeronautics and applied physics.

    Collaborating with Katia Bertoldi, Jennifer Lewis, and Jordan Raney of Harvard University, Kochmann, Daraio, and Caltech graduate student Neel Nadkarni designed chains of the bistable elements, connected to one another by springs. When one link “pops” from the concave to the convex state, its spring tugs at the link that is next downstream in the chain, popping it to a convex position as well. The signal travels unidirectionally down the chain. The energy released by the popping balances out any energy absorbed by the soft material, allowing the process to continue down the chain across long distances and at constant speed.

    A proof-of-concept version of the design constructed from 3-D printed elements is described in a paper published August 8, 2016 in the Proceedings of the National Academy of Sciences. This paper was the third in the series of publications outlining the new concept for transmitting signals. It outlined how the design can be used to build mechanical AND and OR logic gates such as those used in computer processors. Logic gates are the building blocks of circuits, allowing signals to be processed.

    “These systems could be used as actuators to control robotic limbs, while passively performing simple logic decisions,” Daraio says. Actuators use the transfer of energy to perform mechanical work, and in this case, the transfer of energy would occur via a mechanical rather than an electrical system.

    The first paper in the series was published in March in the journal Physical Review B, and it described Kochmann’s theoretical, mathematical framework for the system. The second paper was published in Physical Review Letters in June, and it describes Daraio’s first experimental model for the system.

    While springs can be employed between the bistable elements, the team also demonstrated in the Physical Review Letters paper how magnets could be used to connect the elements—potentially allowing the chain to be reset to its original position with a reversal of polarity.

    “Though there are many applications, the fundamental principles that we explore are most exciting to me,” Kochmann says. “These nonlinear systems show very similar behavior to materials at the atomic scale but these are difficult to access experimentally or computationally. Now we have built a simple macroscale analogue that mimics how they behave.”

    The PNAS paper is titled Stable propogation of mechanical signals in soft media using stored elastic energy. The authors are Nadkarni, Daraio, and Kochmann of Caltech and Jordan Raney, Jennifer Lewis, and Katia Bertoldi of Harvard University. The work was funded by the National Science Foundation.

    See the full article here .

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    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”
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