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  • richardmitnick 1:52 pm on April 13, 2015 Permalink | Reply
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    From Caltech: “Explaining Saturn’s Great White Spots” 

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    Caltech

    04/13/2015
    Kathy Svitil

    1
    This image, taken by NASA’s Cassini spacecraft in February 2011, shows a huge storm in Saturn’s northern hemisphere.
    Credit: NASA/JPL-Caltech/Space Science Institute

    Every 20 to 30 years, Saturn’s atmosphere roils with giant, planet-encircling thunderstorms that produce intense lightning and enormous cloud disturbances. The head of one of these storms—popularly called “great white spots,” in analogy to the Great Red Spot of Jupiter—can be as large as Earth. Unlike Jupiter’s spot, which is calm at the center and has no lightning, the Saturn spots are active in the center and have long tails that eventually wrap around the planet.

    Six such storms have been observed on Saturn over the past 140 years, alternating between the equator and midlatitudes, with the most recent emerging in December 2010 and encircling the planet within six months. The storms usually occur when Saturn’s northern hemisphere is most tilted toward the sun. Just what triggers them and why they occur so infrequently, however, has been unclear.

    Now, a new study by two Caltech planetary scientists suggests a possible cause for these storms. The study was published April 13 in the advance online issue of the journal Nature Geoscience.

    Using numerical modeling, Professor of Planetary Science Andrew Ingersoll and his graduate student Cheng Li simulated the formation of the storms and found that they may be caused by the weight of the water molecules in the planet’s atmosphere. Because these water molecules are heavy compared to the hydrogen and helium that comprise most of the gas-giant planet’s atmosphere, they make the upper atmosphere lighter when they rain out, and that suppresses convection.

    Over time, this leads to a cooling of the upper atmosphere. But that cooling eventually overrides the suppressed convection, and warm moist air rapidly rises and triggers a thunderstorm. “The upper atmosphere is so cold and so massive that it takes 20 to 30 years for this cooling to trigger another storm,” says Ingersoll.

    Ingersoll and Li found that this mechanism matches observations of the great white spot of 2010 taken by NASA’s Cassini spacecraft, which has been observing Saturn and its moons since 2004.

    NASA Cassini Spacecraft
    Cassini

    The researchers also propose that the absence of planet-encircling storms on Jupiter could be explained if Jupiter’s atmosphere contains less water vapor than Saturn’s atmosphere. That is because saturated gas (gas that contains the maximum amount of moisture that it can hold at a particular temperature) in a hydrogen-helium atmosphere goes through a density minimum as it cools. That is, it first becomes less dense as the water precipitates out, and then it becomes more dense as cooling proceeds further. “Going through that minimum is key to suppressing the convection, but there has to be enough water vapor to start with,” says Li.

    Ingersoll and Li note that observations by the Galileo spacecraft and the Hubble Space Telescope indicate that Saturn does indeed have enough water to go through this density minimum, whereas Jupiter does not. In November 2016, NASA’s Juno spacecraft, now en route to Jupiter, will start measuring the water abundance on that planet. “That should help us understand not only the meteorology but also the planet’s formation, since water is expected to be the third most abundant molecule after hydrogen and helium in a giant planet atmosphere,” Ingersoll says.

    NASA Galileo
    Galileo

    NASA Hubble Telescope
    NASA/ESA Hubble

    NASA Juno
    Juno

    The work in the paper, Moist convection in hydrogen atmospheres and the frequency of Saturn’s giant storms, was supported by the National Science Foundation and the Cassini Project of NASA.

    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 2:02 pm on March 30, 2015 Permalink | Reply
    Tags: , , Caltech, , , NANOGrave,   

    From Caltech: “New NSF-Funded Physics Frontiers Center Expands Hunt for Gravitational Waves” 

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    Caltech

    03/30/2015
    Kathy Svitil

    1
    Gravitational waves are ripples in space-time (represented by the green grid) produced by interacting supermassive black holes in distant galaxies. As these waves wash over the Milky Way, they cause minute yet measurable changes in the arrival times at Earth of the radio signals from pulsars, the Universe’s most stable natural clocks. These telltale changes can be detected by sensitive radio telescopes, like the Arecibo Observatory in Puerto Rico and the Green Bank Telescope in West Virginia. Credit: David Champion

    The search for gravitational waves—elusive ripples in the fabric of space-time predicted to arise from extremely energetic and large-scale cosmic events such as the collisions of neutron stars and black holes—has expanded, thanks to a $14.5-million, five-year award from the National Science Foundation for the creation and operation of a multi-institution Physics Frontiers Center (PFC) called the North American Nanohertz Observatory for Gravitational Waves (NANOGrav).

    The NANOGrav PFC will be directed by Xavier Siemens, a physicist at the University of Wisconsin–Milwaukee and the principal investigator for the project, and will fund the NANOGrav research activities of 55 scientists and students distributed across the 15-institution collaboration, including the work of four Caltech/JPL scientists—Senior Faculty Associate Curt Cutler; Visiting Associates Joseph Lazio and Michele Vallisneri; and Walid Majid, a visiting associate at Caltech and a JPL research scientist—as well as two new postdoctoral fellows at Caltech to be supported by the PFC funds. JPL is managed by Caltech for NASA.

    “Caltech has a long tradition of leadership in both the theoretical prediction of sources of gravitational waves and experimental searches for them,” says Sterl Phinney, professor of theoretical astrophysics and executive officer for astronomy in the Division of Physics, Mathematics and Astronomy. “This ranges from waves created during the inflation of the early universe, which have periods of billions of years; to waves from supermassive black hole binaries in the nuclei of galaxies, with periods of years; to a multitude of sources with periods of minutes to hours; to the final inspiraling of neutron stars and stellar mass black holes, which create gravitational waves with periods less than a tenth of a second.”

    The detection of the high-frequency gravitational waves created in this last set of events is a central goal of Advanced LIGO (the next-generation Laser Interferometry Gravitational-Wave Observatory), scheduled to begin operation later in 2015. LIGO and Advanced LIGO, funded by NSF, are comanaged by Caltech and MIT.

    “This new Physics Frontier Center is a significant boost to what has long been the dark horse in the exploration of the spectrum of gravitational waves: low-frequency gravitational waves,” Phinney says. These gravitational waves are predicted to have such a long wavelength—significantly larger than our solar system—that we cannot build a detector large enough to observe them. Fortunately, the universe itself has created its own detection tool, millisecond pulsars—the rapidly spinning, superdense remains of massive stars that have exploded as supernovas. These ultrastable stars appear to “tick” every time their beamed emissions sweep past Earth like a lighthouse beacon. Gravitational waves may be detected in the small but perceptible fluctuations—a few tens of nanoseconds over five or more years—they cause in the measured arrival times at Earth of radio pulses from these millisecond pulsars.

    NANOGrav makes use of the Arecibo Observatory in Puerto Rico and the National Radio Astronomy Observatory’s Green Bank Telescope (GBT), and will obtain other data from telescopes in Europe, Australia, and Canada. The team of researchers at Caltech will lead NANOGrav’s efforts to develop the approaches and algorithms for extracting the weak gravitational-wave signals from the minute changes in the arrival times of pulses from radio pulsars that are observed regularly by these instruments.

    Arecibo Observatory
    Arecibo Radio Observatory Telescope

    NRAO GBT
    NRAO/GBT

    See the full article here.

    Please help promote STEM in your local schools.

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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 5:17 am on March 24, 2015 Permalink | Reply
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    From Caltech: “New Research Suggests Solar System May Have Once Harbored Super-Earths” 

    Caltech Logo
    Caltech

    03/23/2015
    Kimm Fesenmaier

    Caltech and UC Santa Cruz Researchers Say Earth Belongs to a Second Generation of Planets

    1
    This snapshot from a new simulation depicts a time early in the solar system’s history when Jupiter likely made a grand inward migration (here, Jupiter’s orbit is the thick white circle). As it moved inward, Jupiter picked up primitive planetary building blocks, or planetesimals, and drove them into eccentric orbits (turquoise) that overlapped the unperturbed part of the planetary disk (yellow), setting off a cascade of collisions that would have ushered any interior planets into the sun.
    Credit: K.Batygin/Caltech

    Long before Mercury, Venus, Earth, and Mars formed, it seems that the inner solar system may have harbored a number of super-Earths—planets larger than Earth but smaller than Neptune. If so, those planets are long gone—broken up and fallen into the sun billions of years ago largely due to a great inward-and-then-outward journey that Jupiter made early in the solar system’s history.

    This possible scenario has been suggested by Konstantin Batygin, a Caltech planetary scientist, and Gregory Laughlin of UC Santa Cruz in a paper that appears the week of March 23 in the online edition of the Proceedings of the National Academy of Sciences (PNAS). The results of their calculations and simulations suggest the possibility of a new picture of the early solar system that would help to answer a number of outstanding questions about the current makeup of the solar system and of Earth itself. For example, the new work addresses why the terrestrial planets in our solar system have such relatively low masses compared to the planets orbiting other sun-like stars.

    “Our work suggests that Jupiter’s inward-outward migration could have destroyed a first generation of planets and set the stage for the formation of the mass-depleted terrestrial planets that our solar system has today,” says Batygin, an assistant professor of planetary science. “All of this fits beautifully with other recent developments in understanding how the solar system evolved, while filling in some gaps.”

    Thanks to recent surveys of exoplanets—planets in solar systems other than our own—we know that about half of sun-like stars in our galactic neighborhood have orbiting planets. Yet those systems look nothing like our own. In our solar system, very little lies within Mercury’s orbit; there is only a little debris—probably near-Earth asteroids that moved further inward—but certainly no planets. That is in sharp contrast with what astronomers see in most planetary systems. These systems typically have one or more planets that are substantially more massive than Earth orbiting closer to their suns than Mercury does, but very few objects at distances beyond.

    “Indeed, it appears that the solar system today is not the common representative of the galactic planetary census. Instead we are something of an outlier,” says Batygin. “But there is no reason to think that the dominant mode of planet formation throughout the galaxy should not have occurred here. It is more likely that subsequent changes have altered its original makeup.”

    According to Batygin and Laughlin, Jupiter is critical to understanding how the solar system came to be the way it is today. Their model incorporates something known as the Grand Tack scenario, which was first posed in 2001 by a group at Queen Mary University of London and subsequently revisited in 2011 by a team at the Nice Observatory. That scenario says that during the first few million years of the solar system’s lifetime, when planetary bodies were still embedded in a disk of gas and dust around a relatively young sun, Jupiter became so massive and gravitationally influential that it was able to clear a gap in the disk. And as the sun pulled the disk’s gas in toward itself, Jupiter also began drifting inward, as though carried on a giant conveyor belt.

    “Jupiter would have continued on that belt, eventually being dumped onto the sun if not for Saturn,” explains Batygin. Saturn formed after Jupiter but got pulled toward the sun at a faster rate, allowing it to catch up. Once the two massive planets got close enough, they locked into a special kind of relationship called an orbital resonance, where their orbital periods were rational—that is, expressible as a ratio of whole numbers. In a 2:1 orbital resonance, for example, Saturn would complete two orbits around the sun in the same amount of time that it took Jupiter to make a single orbit. In such a relationship, the two bodies would begin to exert a gravitational influence on one another.

    “That resonance allowed the two planets to open up a mutual gap in the disk, and they started playing this game where they traded angular momentum and energy with one another, almost to a beat,” says Batygin. Eventually, that back and forth would have caused all of the gas between the two worlds to be pushed out, a situation that would have reversed the planets’ migration direction and sent them back outward in the solar system. (Hence, the “tack” part of the Grand Tack scenario: the planets migrate inward and then change course dramatically, something like a boat tacking around a buoy.)

    In an earlier model developed by Bradley Hansen at UCLA, the terrestrial planets conveniently end up in their current orbits with their current masses under a particular set of circumstances—one in which all of the inner solar system’s planetary building blocks, or planetesimals, happen to populate a narrow ring stretching from 0.7 to 1 astronomical unit (1 astronomical unit is the average distance from the sun to Earth), 10 million years after the sun’s formation. According to the Grand Tack scenario, the outer edge of that ring would have been delineated by Jupiter as it moved toward the sun on its conveyor belt and cleared a gap in the disk all the way to Earth’s current orbit.

    But what about the inner edge? Why should the planetesimals be limited to the ring on the inside? “That point had not been addressed,” says Batygin.

    He says the answer could lie in primordial super-Earths. The empty hole of the inner solar system corresponds almost exactly to the orbital neighborhood where super-Earths are typically found around other stars. It is therefore reasonable to speculate that this region was cleared out in the primordial solar system by a group of first-generation planets that did not survive.

    Batygin and Laughlin’s calculations and simulations show that as Jupiter moved inward, it pulled all the planetesimals it encountered along the way into orbital resonances and carried them toward the sun. But as those planetesimals got closer to the sun, their orbits also became elliptical. “You cannot reduce the size of your orbit without paying a price, and that turns out to be increased ellipticity,” explains Batygin. Those new, more elongated orbits caused the planetesimals, mostly on the order of 100 kilometers in radius, to sweep through previously unpenetrated regions of the disk, setting off a cascade of collisions among the debris. In fact, Batygin’s calculations show that during this period, every planetesimal would have collided with another object at least once every 200 years, violently breaking them apart and sending them decaying into the sun at an increased rate.

    The researchers did one final simulation to see what would happen to a population of super-Earths in the inner solar system if they were around when this cascade of collisions started. They ran the simulation on a well-known extrasolar system known as Kepler-11, which features six super-Earths with a combined mass 40 times that of Earth, orbiting a sun-like star. The result? The model predicts that the super-Earths would be shepherded into the sun by a decaying avalanche of planetesimals over a period of 20,000 years.

    “It’s a very effective physical process,” says Batygin. “You only need a few Earth masses worth of material to drive tens of Earth masses worth of planets into the sun.”

    Batygin notes that when Jupiter tacked around, some fraction of the planetesimals it was carrying with it would have calmed back down into circular orbits. Only about 10 percent of the material Jupiter swept up would need to be left behind to account for the mass that now makes up Mercury, Venus, Earth, and Mars.

    From that point, it would take millions of years for those planetesimals to clump together and eventually form the terrestrial planets—a scenario that fits nicely with measurements that suggest that Earth formed 100–200 million years after the birth of the sun. Since the primordial disk of hydrogen and helium gas would have been long gone by that time, this could also explain why Earth lacks a hydrogen atmosphere. “We formed from this volatile-depleted debris,” says Batygin.

    And that sets us apart in another way from the majority of exoplanets. Batygin expects that most exoplanets—which are mostly super-Earths—have substantial hydrogen atmospheres, because they formed at a point in the evolution of their planetary disk when the gas would have still been abundant. “Ultimately, what this means is that planets truly like Earth are intrinsically not very common,” he says.

    The paper also suggests that the formation of gas giant planets such as Jupiter and Saturn—a process that planetary scientists believe is relatively rare—plays a major role in determining whether a planetary system winds up looking something like our own or like the more typical systems with close-in super-Earths. As planet hunters identify additional systems that harbor gas giants, Batygin and Laughlin will have more data against which they can check their hypothesis—to see just how often other migrating giant planets set off collisional cascades in their planetary systems, sending primordial super-Earths into their host stars.

    The researchers describe their work in a paper titled Jupiter’s Decisive Role in the Inner Solar System’s Early Evolution.

    See the full article here.

    Please help promote STEM in your local schools.

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    Stem Education Coalition

    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 3:52 pm on March 9, 2015 Permalink | Reply
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    From Caltech: “One Step Closer to Artificial Photosynthesis and “Solar Fuels” 

    Caltech Logo
    Caltech

    03/09/2015
    Ker Than

    1
    Ke Sun, a Caltech postdoc in the lab of George L. Argyros Professor and Professor of Chemistry Nate Lewis, peers into a sample of a new, protective film that he has helped develop to aid in the process of harnessing sunlight to generate fuels.
    Credit: Lance Hayashida/Caltech Marcomm

    Caltech scientists, inspired by a chemical process found in leaves, have developed an electrically conductive film that could help pave the way for devices capable of harnessing sunlight to split water into hydrogen fuel.

    When applied to semiconducting materials such as silicon, the nickel oxide film prevents rust buildup and facilitates an important chemical process in the solar-driven production of fuels such as methane or hydrogen.

    “We have developed a new type of protective coating that enables a key process in the solar-driven production of fuels to be performed with record efficiency, stability, and effectiveness, and in a system that is intrinsically safe and does not produce explosive mixtures of hydrogen and oxygen,” says Nate Lewis, the George L. Argyros Professor and professor of chemistry at Caltech and a coauthor of a new study, published the week of March 9 in the online issue of the journal the Proceedings of the National Academy of Sciences, that describes the film.

    The development could help lead to safe, efficient artificial photosynthetic systems—also called solar-fuel generators or “artificial leaves”—that replicate the natural process of photosynthesis that plants use to convert sunlight, water, and carbon dioxide into oxygen and fuel in the form of carbohydrates, or sugars.

    The artificial leaf that Lewis’ team is developing in part at Caltech’s Joint Center for Artificial Photosynthesis (JCAP) consists of three main components: two electrodes—a photoanode and a photocathode—and a membrane. The photoanode uses sunlight to oxidize water molecules to generate oxygen gas, protons, and electrons, while the photocathode recombines the protons and electrons to form hydrogen gas. The membrane, which is typically made of plastic, keeps the two gases separate in order to eliminate any possibility of an explosion, and lets the gas be collected under pressure to safely push it into a pipeline.

    Scientists have tried building the electrodes out of common semiconductors such as silicon or gallium arsenide—which absorb light and are also used in solar panels—but a major problem is that these materials develop an oxide layer (that is, rust) when exposed to water.

    Lewis and other scientists have experimented with creating protective coatings for the electrodes, but all previous attempts have failed for various reasons. “You want the coating to be many things: chemically compatible with the semiconductor it’s trying to protect, impermeable to water, electrically conductive, highly transparent to incoming light, and highly catalytic for the reaction to make oxygen and fuels,” says Lewis, who is also JCAP’s scientific director. “Creating a protective layer that displayed any one of these attributes would be a significant leap forward, but what we’ve now discovered is a material that can do all of these things at once.”

    The team has shown that its nickel oxide film is compatible with many different kinds of semiconductor materials, including silicon, indium phosphide, and cadmium telluride. When applied to photoanodes, the nickel oxide film far exceeded the performance of other similar films—including one that Lewis’s group created just last year. That film was more complicated—it consisted of two layers versus one and used as its main ingredient titanium dioxide (TiO2, also known as titania), a naturally occurring compound that is also used to make sunscreens, toothpastes, and white paint.

    “After watching the photoanodes run at record performance without any noticeable degradation for 24 hours, and then 100 hours, and then 500 hours, I knew we had done what scientists had failed to do before,” says Ke Sun, a postdoc in Lewis’s lab and the first author of the new study.

    Lewis’s team developed a technique for creating the nickel oxide film that involves smashing atoms of argon into a pellet of nickel atoms at high speeds, in an oxygen-rich environment. “The nickel fragments that sputter off of the pellet react with the oxygen atoms to produce an oxidized form of nickel that gets deposited onto the semiconductor,” Lewis says.

    Crucially, the team’s nickel oxide film works well in conjunction with the membrane that separates the photoanode from the photocathode and staggers the production of hydrogen and oxygen gases.

    “Without a membrane, the photoanode and photocathode are close enough to each other to conduct electricity, and if you also have bubbles of highly reactive hydrogen and oxygen gases being produced in the same place at the same time, that is a recipe for disaster,” Lewis says. “With our film, you can build a safe device that will not explode, and that lasts and is efficient, all at once.”

    Lewis cautions that scientists are still a long way off from developing a commercial product that can convert sunlight into fuel. Other components of the system, such as the photocathode, will also need to be perfected.

    “Our team is also working on a photocathode,” Lewis says. “What we have to do is combine both of these elements together and show that the entire system works. That will not be easy, but we now have one of the missing key pieces that has eluded the field for the past half-century.”

    Along with Lewis and Sun, additional authors on the paper, “Stable solar-driven oxidation of water by semiconducting photoanodes protected by transparent catalytic nickel oxide films,” include Caltech graduate students Fadl Saadi, Michael Lichterman, Xinghao Zhou, Noah Plymale, and Stefan Omelchenko; William Hale, from the University of Southampton; Hsin-Ping Wang and Jr-Hau He, from King Abdullah University in Saudi Arabia; Kimberly Papadantonakis, a scientific research manager at Caltech; and Bruce Brunschwig, the director of the Molecular Materials Research Center at Caltech. Funding was provided by the Office of Science at the U.S. Department of Energy, the National Science Foundation, the Beckman Institute, and the Gordon and Betty Moore Foundation.

    See the full article here.

    Please help promote STEM in your local schools.

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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 3:19 pm on February 13, 2015 Permalink | Reply
    Tags: , Caltech, Iron,   

    From Caltech: “How Iron Feels the Heat” 

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    Caltech

    02/13/2015
    Jessica Stoller-Conrad

    1

    As you heat up a piece of iron, the arrangement of the iron atoms changes several times before melting. This unusual behavior is one reason why steel, in which iron plays a starring role, is so sturdy and ubiquitous in everything from teapots to skyscrapers. But the details of just how and why iron takes on so many different forms have remained a mystery. Recent work at Caltech in the Division of Engineering and Applied Science, however, provides evidence for how iron’s magnetism plays a role in this curious property—an understanding that could help researchers develop better and stronger steel.

    “Humans have been working with regular old iron for thousands of years, but this is a piece about its thermodynamics that no one has ever really understood,” says Brent Fultz, the Barbara and Stanley R. Rawn, Jr., Professor of Materials Science and Applied Physics.

    The laws of thermodynamics govern the natural behavior of materials, such as the temperature at which water boils and the timing of chemical reactions. These same principles also determine how atoms in solids are arranged, and in the case of iron, nature changes its mind several times at high temperatures. At room temperature, the iron atoms are in an unusual loosely packed open arrangement; as iron is heated past 912 degrees Celsius, the atoms become more closely packed before loosening again at 1,394 degrees Celsius and ultimately melting at 1,538 degrees Celsius.

    Iron is magnetic at room temperature, and previous work predicted that iron’s magnetism favors its open structure at low temperatures, but at 770 degrees Celsius iron loses its magnetism. However, iron maintains its open structure for more than a hundred degrees beyond this magnetic transition. This led the researchers to believe that there must be something else contributing to iron’s unusual thermodynamic properties.

    For this missing link, graduate student Lisa Mauger and her colleagues needed to turn up the heat. Solids store heat as small atomic vibrations—vibrations that create disorder, or entropy. At high temperatures, entropy dominates thermodynamics, and atomic vibrations are the largest source of entropy in iron. By studying how these vibrations change as the temperature goes up and magnetism is lost, the researchers hoped to learn more about what is driving these structural rearrangements.

    To do this, the team took its samples of iron to the High Pressure Collaborative Access Team beamline of the Advanced Photon Source [APS] at Argonne National Laboratory [ANL] in Argonne, Illinois. This synchrotron facility produces intense flashes of x-rays that can be tuned to detect the quantum particles of atomic vibration—called phonon excitations—in iron.

    ANL APS
    ANL APS interior
    APS at ANL

    When coupling these vibrational measurements with previously known data about the magnetic behavior of iron at these temperatures, the researchers found that iron’s vibrational entropy was much larger than originally suspected. In fact, the excess was similar to the entropy contribution from magnetism—suggesting that magnetism and atomic vibrations interact synergistically at moderate temperatures. This excess entropy increases the stability of the iron’s open structure even as the sample is heated past the magnetic transition.

    The technique allowed the researchers to conclude, experimentally and for the first time, that magnons—the quantum particles of electron spin (magnetism)—and phonons interact to increase iron’s stability at high temperatures.

    Because the Caltech group’s measurements matched up with the theoretical calculations that were simultaneously being developed by collaborators in the laboratory of Jörg Neugebauer at the Max-Planck-Institut für Eisenforschung GmbH (MPIE), Mauger’s results also contributed to the validation of a new computational model.

    “It has long been speculated that the structural stability of iron is strongly related to an inherent coupling between magnetism and atomic motion,” says Fritz Körmann, postdoctoral fellow at MPIE and the first author on the computational paper. “Actually finding this coupling, and that the data of our experimental colleagues and our own computational results are in such an excellent agreement, was indeed an exciting moment.”

    “Only by combining methods and expertise from various scientific fields such as quantum mechanics, statistical mechanics, and thermodynamics, and by using incredibly powerful supercomputers, it became possible to describe the complex dynamic phenomena taking place inside one of the technologically most used structural materials,” says Neugebauer. “The newly gained insight of how thermodynamic stability is realized in iron will help to make the design of new steels more systematic.”

    For thousands of years, metallurgists have been working to make stronger steels in much the same way that you’d try to develop a recipe for the world’s best cookie: guess and check. Steel begins with a base of standard ingredients—iron and carbon—much like a basic cookie batter begins with flour and butter. And just as you’d customize a cookie recipe by varying the amounts of other ingredients like spices and nuts, the properties of steel can be tuned by adding varying amounts of other elements, such as chromium and nickel.

    With a better computational model for the thermodynamics of iron at different temperatures—one that takes into account the effects of both magnetism and atomic vibrations—metallurgists will now be able to more accurately predict the thermodynamic properties of iron alloys as they alter their recipes.

    The experimental work was published in a paper titled Nonharmonic Phonons in α-Iron at High Temperatures,” in the journal Physical Review B. In addition to Fultz and first author Mauger, other Caltech coauthors include Jorge Alberto Muñoz (PhD ’13) and graduate student Sally June Tracy. The computational paper, Temperature Dependent Magnon-Phonon Coupling in bcc Fe from Theory and Experiment, was coauthored by Fultz and Mauger, led by researchers at the Max Planck Institute, and published in the journal Physical Review Letters. Fultz’s and Mauger’s work was supported by funding from the U.S. Department of Energy.

    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 4:09 pm on February 12, 2015 Permalink | Reply
    Tags: , Caltech,   

    From Caltech: “Caltech biochemist sheds light on structure of key cellular ‘gatekeeper'” 

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    Caltech

    02/12/2015
    Jon Nalick

    1

    Facing a challenge akin to solving a 1,000-piece jigsaw puzzle while blindfolded—and without touching the pieces—many structural biochemists thought it would be impossible to determine the atomic structure of a massive cellular machine called the nuclear pore complex (NPC), which is vital for cell survival.

    But after 10 years of attacking the problem, a team led by André Hoelz, assistant professor of chemistry, recently solved almost a third of the puzzle. The approach his team developed to do so also promises to speed completion of the remainder.

    In an article published online February 12 by Science Express, Hoelz and his colleagues describe the structure of a significant portion of the NPC, which is made up of many copies of about 34 different proteins, perhaps 1,000 proteins in all and a total of 10 million atoms. In eukaryotic cells (those with a membrane-bound nucleus), the NPC forms a transport channel in the nuclear membrane. The NPC serves as a gatekeeper, essentially deciding which proteins and other molecules are permitted to pass into and out of the nucleus. The survival of cells is dependent upon the accuracy of these decisions.

    Understanding the structure of the NPC could lead to new classes of cancer drugs as well as antiviral medicines. “The NPC is a huge target of viruses,” Hoelz says. Indeed, pathogens such as HIV and Ebola subvert the NPC as a way to take control of cells, rendering them incapable of functioning normally. Figuring out just how the NPC works might enable the design of new drugs to block such intruders.

    “This is an incredibly important structure to study,” he says, “but because it is so large and complex, people thought it was crazy to work on it. But 10 years ago, we hypothesized that we could solve the atomic structure with a divide-and-conquer approach—basically breaking the task into manageable parts—and we’ve shown that for a major section of the NPC, this actually worked.”

    To map the structure of the NPC, Hoelz relied primarily on X-ray crystallography, which involves shining X-rays on a crystallized sample and using detectors to analyze the pattern of rays reflected off the atoms in the crystal.

    It is particularly challenging to obtain X-ray diffraction images of the intact NPC for several reasons, including that the NPC is both enormous (about 30 times larger than the ribosome, a large cellular component whose structure wasn’t solved until the year 2000) and complex (with as many as 1,000 individual pieces, each composed of several smaller sections). In addition, the NPC is flexible, with many moving parts, making it difficult to capture in individual snapshots at the atomic level, as X-ray crystallography aims to do. Finally, despite being enormous compared to other cellular components, the NPC is still vanishingly small (only 120 nanometers wide, or about 1/900th the thickness of a dollar bill), and its highly flexible nature prohibits structure determination with current X-ray crystallography methods.

    To overcome those obstacles, Hoelz and his team chose to determine the structure of the coat nucleoporin complex (CNC)—one of the two main complexes that make up the NPC—rather than tackling the whole structure at once (in total the NPC is composed of six subcomplexes, two major ones and four smaller ones, see illustration). He enlisted the support of study coauthor Anthony Kossiakoff of the University of Chicago, who helped to develop the engineered antibodies needed to essentially “superglue” the samples into place to form an ordered crystalline lattice so they could be properly imaged. The X-ray diffraction data used for structure determination was collected at the General Medical Sciences and National Cancer Institutes Structural Biology Beamline at the Argonne National Laboratory.

    With the help of Caltech’s Molecular Observatory—a facility, developed with support from the Gordon and Betty Moore Foundation, that includes a completely automated X-ray beamline at the Stanford Synchrotron Radiation Laboratory that can be controlled remotely from Caltech—Hoelz’s team refined the antibody adhesives required to generate the best crystalline samples. This process alone took two years to get exactly right.

    Hoelz and his team were able to determine the precise size, shape, and the position of all atoms of the CNC, and also its location within the entire NPC.

    The CNC is not the first component of the NPC to be fully characterized, but it is by far the largest. Hoelz says that once the other major component—known as the adaptor–channel nucleoporin complex—and the four smaller subcomplexes are mapped, the NPC’s structure will be fully understood.

    The CNC that Hoelz and his team evaluated comes from baker’s yeast—a commonly used research organism—but the CNC structure is the right size and shape to dock with the NPC of a human cell. “It fits inside like a hand in a glove,” Hoelz says. “That’s significant because it is a very strong indication that the architecture of the NPC in both are probably the same and that the machinery is so important that evolution has not changed it in a billion years.”

    Being able to successfully determine the structure of the CNC makes mapping the remainder of the NPC an easier proposition. “It’s like climbing Mount Everest. Knowing you can do it lowers the bar, so you know you can now climb K2 and all these other mountains,” says Hoelz, who is convinced that the entire NPC will be characterized soon. “It will happen. I don’t know if it will be in five or 10 or 20 years, but I’m sure it will happen in my lifetime. We will have an atomic model of the entire nuclear pore.”

    Still, he adds, “My dream actually goes much farther. I don’t really want to have a static image of the pore. What I really would like—and this is where people look at me with a bit of a smile on their face, like they’re laughing a little bit—is to get an image of how the pore is moving, how the machine actually works. The pore is not a static hole, it can open up like the iris of a camera to let something through that’s much bigger. How does it do it?”

    To understand that machine in motion, he adds, “you don’t just need one snapshot, you need multiple snapshots. But once you have one, you can infer the other ones much quicker, so that’s the ultimate goal. That’s the dream.”

    Along with Hoelz, additional Caltech authors on the paper, Architecture of the Nuclear Pore Complex Coat, include postdoctoral scholars Tobias Stuwe and Ana R. Correia, and graduate student Daniel H. Lin. Coauthors from the University of Chicago Department of Biochemistry and Molecular Biology include Anthony Kossiakoff, Marcin Paduch and Vincent Lu. The work was supported by Caltech startup funds, the Albert Wyrick V Scholar Award of the V Foundation for Cancer Research, the 54th Mallinckrodt Scholar Award of the Edward Mallinckrodt, Jr. Foundation, and a Kimmel Scholar Award of the Sidney Kimmel Foundation for Cancer Research.

    See the full article here.

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  • richardmitnick 4:15 pm on January 21, 2015 Permalink | Reply
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    From Caltech: “Size Matters: The Importance of Building Small Things” 

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    Caltech

    01/21/2015
    Watson Lecture Preview

    Strong materials, such as concrete, are usually heavy, and lightweight materials, such as rubber (for latex gloves) and paper, are usually weak and susceptible to tearing and damage. Julia R. Greer, professor of materials science and mechanics in Caltech’s Division of Engineering and Applied Science, is helping to break that linkage.

    Q: What do you do?

    A: I’m a materials scientist, and I work with materials whose dimensions are at the nanoscale. A nanometer is one-billionth of a meter, or about one-hundred-thousandth the diameter of a hair. At those dimensions, ordinary materials such as metals, ceramics, and glasses take on properties quite unlike their bulk-scale counterparts. Many materials become 10 or more times stronger. Some become damage-tolerant. Glass shatters very easily in our world, for example, but at the nanoscale, some glasses become deformable and less breakable. We’re trying to harness these so-called size effects to create “meta-materials” that display these properties at scales we can see.

    We can fabricate essentially any structure we like with the help of a special instrument that is like a tabletop microprinter, but uses laser pulses to “write” a three-dimensional structure into a tiny droplet of a polymer. The laser “sets” the polymer into our three-dimensional design, creating a minuscule plastic scaffold. We rinse away the unset polymer and put our scaffold in another machine that essentially wraps it in a very thin, nanometers-thick ribbon of the stuff we’re actually interested in—a metal, a semiconductor, or a biocompatible material. Then we get rid of the plastic, leaving just the interwoven hollow tubular structure. The final structure is hollow, and it weighs nothing. It’s 99.9 percent air.

    We can even make structures nested within other structures. We recently started making hierarchical nanotrusses—trusses built from smaller trusses, like a fractal.

    1
    A fractal nanotruss made in Greer’s lab.
    Credit: Lucas Meza, Greer lab/Caltech

    Q: How big can you make these things, and where might that lead us?

    A: Right now, most of them are about 100 by 100 by 100 microns cubed. A micron is a millionth of a meter, so that is very small. And the unit cells, the individual building blocks, are very, very small—a few microns each. I recently asked my graduate students to create a demo big enough to be visible, so I could show it at seminars. They wrote me an object about 6 millimeters by 6 millimeters by about 100 microns tall. It took them about a week just to write the polymer, never mind the ribbon deposition and all the other steps.

    The demo piece looks like a little white square from the top, until you hold it up to the light. Then a rainbow of colors play across its surface, and it looks like a fine opal. That’s because the nanolattices and the opals are both photonic crystals, which means that their unit cells are the right size to interact with light. Synthetic three-dimensional photonic crystals are relatively hard to make, but they could be extremely useful as high-speed switches for fiber-optic networks.

    Our goal is to figure out a way to mass produce nanostructures that are big enough to see. The possibilities are endless. You could make a soft contact lens that can’t be torn, for example. Or a very lightweight, very safe biocompatible material that could go into someone’s body as a scaffold on which to grow cells. Or you could use semiconductors to build 3-D logic circuits. We’re working with Assistant Professor of Applied Physics and Materials Science Andrei Faraon [BS ’04] to try to figure out how to simultaneously write a whole bunch of things that are all 1 centimeter by 1 centimeter.

    Q: How did you get into this line of work? What got you started?

    A: When I first got to Caltech, I was working on metallic nanopillars. That was my bread and butter. Nanopillars are about 50 nanometers to 1 micron in diameter, and about three times taller than their width. They were what we used to demonstrate, for example, that smaller becomes stronger—the pillars were stronger than the bulk metal by an order of magnitude, which is nothing to laugh at.

    Nanopillars are awesome, but you can’t build anything out of them. And so I always wondered if I could use something like them as nano-LEGOs and construct larger objects, like a nano-Eiffel Tower. The question I asked myself was if each individual component had that very, very high strength, would the whole structure be incredibly strong? That was always in the back of my mind. Then I met some people at DARPA (Defense Advanced at HRL (formerly Hughes Research Laboratories) who were interested in some similar questions, specifically about using architecture in material design. My HRL colleagues were making microscale structures called micro-trusses, so we started a very successful DARPA-funded collaboration to make even smaller trusses with unit cells in the micron range. These structures were still far too big for my purposes, but they brought this work closer to reality.

    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 6:47 pm on January 8, 2015 Permalink | Reply
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    From Caltech: “Unusual Light Signal Yields Clues About Elusive Black Hole Merger” 

    Caltech Logo
    Caltech

    01/07/2015
    Ker Than

    The central regions of many glittering galaxies, our own Milky Way included, harbor cores of impenetrable darkness—black holes with masses equivalent to millions, or even billions, of suns. What is more, these supermassive black holes and their host galaxies appear to develop together, or “co-evolve.” Theory predicts that as galaxies collide and merge, growing ever more massive, so too do their dark hearts.

    bh
    Simulation of gravitational lensing by a black hole, which distorts the image of a galaxy in the background


    ESOCast
    Astronomers using ESO’s Very Large Telescope have discovered a gas cloud with several times the mass of the Earth accelerating towards the black hole at the centre of the Milky Way. This is the first time ever that the approach of such a doomed cloud to a supermassive black hole has been observed. This ESOcast explains the new results and includes spectacular simulations of how the cloud will break up over the next few years.
    Credit: ESO.

    ESO VLT Interferometer
    ESO VLT Interior
    ESO/VLT

    Black holes by themselves are impossible to see, but their gravity can pull in surrounding gas to form a swirling band of material called an accretion disk. The spinning particles are accelerated to tremendous speeds and release vast amounts of energy in the form of heat and powerful X-rays and gamma rays. When this process happens to a supermassive black hole, the result is a quasar—an extremely luminous object that outshines all of the stars in its host galaxy and that is visible from across the universe. “Quasars are valuable probes of the evolution of galaxies and their central black holes,” says George Djorgovski, professor of astronomy and director of the Center for Data-Driven Discovery at Caltech.

    In the January 7 issue of the journal Nature, Djorgovski and his collaborators report on an unusual repeating light signal from a distant quasar that they say is most likely the result of two supermassive black holes in the final phases of a merger—something that is predicted from theory but which has never been observed before. The discovery could help shed light on a long-standing conundrum in astrophysics called the “final parsec problem,” which refers to the failure of theoretical models to predict what the final stages of a black hole merger look like or even how long the process might take. “The end stages of the merger of these supermassive black hole systems are very poorly understood,” says the study’s first author, Matthew Graham, a senior computational scientist at Caltech. “The discovery of a system that seems to be at this late stage of its evolution means we now have an observational handle on what is going on.”

    Djorgovski and his team discovered the unusual light signal emanating from quasar PG 1302-102 after analyzing results from the Catalina Real-Time Transient Survey (CRTS), which uses three ground telescopes in the United States and Australia to continuously monitor some 500 million celestial light sources strewn across about 80 percent of the night sky. “There has never been a data set on quasar variability that approaches this scope before,” says Djorgovski, who directs the CRTS. “In the past, scientists who study the variability of quasars might only be able to follow some tens, or at most hundreds, of objects with a limited number of measurements. In this case, we looked at a quarter million quasars and were able to gather a few hundred data points for each one.”

    “Until now, the only known examples of supermassive black holes on their way to a merger have been separated by tens or hundreds of thousands of light years,” says study coauthor Daniel Stern, a scientist at NASA’s Jet Propulsion Laboratory. “At such vast distances, it would take many millions, or even billions, of years for a collision and merger to occur. In contrast, the black holes in PG 1302-102 are, at most, a few hundredths of a light year apart and could merge in about a million years or less.”

    Djorgovski and his team did not set out to find a black hole merger. Rather, they initially embarked on a systematic study of quasar brightness variability in the hopes of finding new clues about their physics. But after screening the data using a pattern-seeking algorithm that Graham developed, the team found 20 quasars that seemed to be emitting periodic optical signals. This was surprising, because the light curves of most quasars are chaotic—a reflection of the random nature by which material from the accretion disk spirals into a black hole. “You just don’t expect to see a periodic signal from a quasar,” Graham says. “When you do, it stands out.”

    Of the 20 periodic quasars that CRTS identified, PG 1302-102 was the best example. It had a strong, clean signal that appeared to repeat every five years or so. “It has a really nice smooth up-and-down signal, similar to a sine wave, and that just hasn’t been seen before in a quasar,” Graham says.

    The team was cautious about jumping to conclusions. “We approached it with skepticism but excitement as well,” says study coauthor Eilat Glikman, an assistant professor of physics at Middlebury College in Vermont. After all, it was possible that the periodicity the scientists were seeing was just a temporary ordered blip in an otherwise chaotic signal. To help rule out this possibility, the scientists pulled in data about the quasar from previous surveys to include in their analysis. After factoring in the historical observations (the scientists had nearly 20 years’ worth of data about quasar PG 1302-102), the repeating signal was, encouragingly, still there.

    The team’s confidence increased further after Glikman analyzed the quasar’s light spectrum. The black holes that scientists believe are powering quasars do not emit light, but the gases swirling around them in the accretion disks are traveling so quickly that they become heated into glowing plasma. “When you look at the emission lines in a spectrum from an object, what you’re really seeing is information about speed—whether something is moving toward you or away from you and how fast. It’s the Doppler effect,” Glikman says. “With quasars, you typically have one emission line, and that line is a symmetric curve. But with this quasar, it was necessary to add a second emission line with a slightly different speed than the first one in order to fit the data. That suggests something else, such as a second black hole, is perturbing this system.”

    Avi Loeb, who chairs the astronomy department at Harvard University, agreed with the team’s assessment that a “tight” supermassive black hole binary is the most likely explanation for the periodic signal they are seeing. “The evidence suggests that the emission originates from a very compact region around the black hole and that the speed of the emitting material in that region is at least a tenth of the speed of light,” says Loeb, who did not participate in the research. “A secondary black hole would be the simplest way to induce a periodic variation in the emission from that region, because a less dense object, such as a star cluster, would be disrupted by the strong gravity of the primary black hole.”

    In addition to providing an unprecedented glimpse into the final stages of a black hole merger, the discovery is also a testament to the power of “big data” science, where the challenge lies not only in collecting high-quality information but also devising ways to mine it for useful information. “We’re basically moving from having a few pictures of the whole sky or repeated observations of tiny patches of the sky to having a movie of the entire sky all the time,” says Sterl Phinney, a professor of theoretical physics at Caltech, who was also not involved in the study. “Many of the objects in the movie will not be doing anything very exciting, but there will also be a lot of interesting ones that we missed before.”

    It is still unclear what physical mechanism is responsible for the quasar’s repeating light signal. One possibility, Graham says, is that the quasar is funneling material from its accretion disk into luminous twin plasma jets that are rotating like beams from a lighthouse. “If the glowing jets are sweeping around in a regular fashion, then we would only see them when they’re pointed directly at us. The end result is a regularly repeating signal,” Graham says.

    Another possibility is that the accretion disk that encircles both black holes is distorted. “If one region is thicker than the rest, then as the warped section travels around the accretion disk, it could be blocking light from the quasar at regular intervals. This would explain the periodicity of the signal that we’re seeing,” Graham says. Yet another possibility is that something is happening to the accretion disk that is causing it to dump material onto the black holes in a regular fashion, resulting in periodic bursts of energy.

    “Even though there are a number of viable physical mechanisms behind the periodicity we’re seeing—either the precessing jet, warped accretion disk or periodic dumping—these are all still fundamentally caused by a close binary system,” Graham says.

    Along with Djorgovski, Graham, Stern, and Glikman, additional authors on the paper, A possible close supermassive black hole binary in a quasar with optical periodicity, include Andrew Drake, a computational scientist and co-principal investigator of the CRTS sky survey at Caltech; Ashish Mahabal, a staff scientist in computational astronomy at Caltech; Ciro Donalek, a computational staff scientist at Caltech; Steve Larson, a senior staff scientist at the University of Arizona; and Eric Christensen, an associate staff scientist at the University of Arizona. Funding for the study was provided by the National Science Foundation.

    See the full article here.

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  • richardmitnick 3:27 pm on December 5, 2014 Permalink | Reply
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    From Caltech: “Einstein Online: An Interview with Diana Kormos-Buchwald” 

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    Caltech

    12/05/2014
    Kimm Fesenmaier

    The Einstein Papers Project, housed at Caltech since 2000, has worked in collaboration with Princeton University Press, the Hebrew University of Jerusalem, and the digital publishing platform Tizra to produce a digital edition of The Collected Papers of Albert Einstein. This new edition presents the world-renowned physicist’s annotated writings and correspondence through 1923 on a free and publicly accessible website.

    ae

    Upon its launch today, the digital papers will contain all 13 published volumes of The Collected Papers, in Einstein’s original German and translated into English, along with an index volume. Additional volumes will be added to the site about 18 months after each new volume is published. The 14th print volume, covering the period from April 1923 through May 1925 and including Einstein’s trip to South America, is scheduled for publication in February 2015.

    We recently sat down with Diana Kormos-Buchwald, professor of history at Caltech and director and general editor of the Einstein Papers Project, to talk about the project’s new digital endeavor.

    The digital edition makes it so that anyone with access to the Internet can read Einstein’s papers and correspondence from the first 44 years of his life for free. Why have you and your colleagues undertaken this massive project?

    The Collected Papers of Albert Einstein is a unique project in and of itself. Einstein is the most revolutionary and famous scientist of the 20th century, and there is no similar integrated project that compiles and annotates a scientist’s writings and correspondence. These scholarly volumes are addressed, in a way, to a specialist audience—the historian of science, the philosopher of science, the physicist who wants to read Einstein in his own words.

    But Einstein is and always has been of great interest to the general public as well. His is the most recognized face on the Internet in all cultures. People are attracted to him because of his creativity, maybe because of his image as an unconventional scientist.

    So we are now making available these volumes that have explanations and footnotes in English, introductions in English, bibliographies, plus full translations, along with the ability to see some of the original manuscripts in high-definition scans through links to the Einstein Archives Online, another project that we launched a few years ago in collaboration with the Hebrew University’s Einstein Archives. We are presenting all of this in an integrated platform in which the user can search for words and phrases in both English and German.

    Biographers and historians need to focus their attention and highlight a selection of documents. But we can present everything—his scientific papers, his letters to his children, his travel diaries, his impressions of foreign lands and cultures, etc.

    I think it’s a great achievement that we were able to put these volumes up without putting them behind a pay wall. The Press has done a wonderful job. Each volume is equivalent to something like 100 scientific papers, plus the translations. And we’re making them free and open. This is a joint effort, and it furthers what I think of as an authoritative way of doing digital humanities.

    What do you hope readers will take away from reading Einstein’s papers?

    What I would hope the reader would find is how extraordinarily hard working Einstein was. Things didn’t happen with flashes of insight. In the famous year 1905, when he publishes his papers on the special theory of relativity, quantum theory, Brownian motion, and E = mc2, he also publishes 20 reviews of other people’s work.

    We’re putting up 5,000 documents. Einstein is known for 5 or 10, maybe 15 major papers; the 5,000 documents provide a context for those well-known papers. He was an extremely productive scientist who wrote two to three pieces per month for the rest of his career, between 1905 and the late 1930s. We have 1,000 writings, many of them unpublished. So the beauty of these volumes is also that they include drafts and writings on a variety of topics that were never published during his lifetime.

    Also, Einstein was interested in a lot of fields of science. He started with great interest in physical chemistry and mastered that literature. And he continued through his entire career to be interested in applied physics, theoretical physics, experimental physics, chemistry, biochemistry. He has exchanges with doctors about physiology. So while Einstein is not a Renaissance figure the way let’s say [Hermann von] Helmholtz was—he is a specialized physicist—nevertheless, he is very curious.

    We also hope to demolish some outstanding myths: Einstein was not the isolated theoretician working by himself in an attic with pen and paper. He was a modern, professional scientist, who earned his living through his work as a scientist and as a professor. He was not wealthy. He was the exemplar of the transformation, if you want, in academia at the end of the 19th century and early 20th century, when science expanded a lot in universities. And the correspondence shows he has this ever-growing circle of friends and colleagues in science and engineering, and young people whom he shepherds and advises.

    How long have you been working on this digital project with Princeton University Press, Tizra, and the Hebrew University of Jerusalem?

    We have been planning this for several years. We wanted to present an accurate rendering of our volumes, which are highly specialized. And we wanted to make these volumes searchable—not only the scholarly annotations but also the scans, facsimiles, and reproductions.

    Einstein famously spent several winter terms here at Caltech in the early 1930s, but the published volumes of The Collected Papers only cover his life through 1923. Are there items referencing Caltech in those volumes that we can look for in the digital edition?

    Yes, Einstein visited Caltech in 1931, ’32, and ’33, but his correspondence with scientists at Caltech goes back much further. For example, in 1913, Einstein wrote a letter to George Ellery Hale asking whether the deflection of sunlight in the sun’s gravitational field could be observed in the daytime. Hale wrote back saying no, we cannot see that.

    He also had contacts with Robert A. Millikan quite early on. In 1922, Millikan officially informed Einstein that the National Academy of Sciences had elected him as a foreign associate. They also discuss scientific work quite a bit, and Millikan and Einstein both serve on the Intellectual Committee for International Cooperation of the League of Nations.

    Einstein was instrumental in recommending several prominent scientists for recruitment very early in the founding of the Institute. The volumes also show correspondence between Einstein, Millikan, and Richard Tolman, professor of physical chemistry and mathematical physics, who was one of the earliest relativists.

    Einstein knows, right at the beginning, in the early 1920s, that Caltech is going to be an exciting place.

    Was Einstein unusual in the size of his correspondence?

    Yes, his correspondence is very large for a scientist. It amounts to about 30,000 items to and from Einstein. It’s of the size of Napoleon’s papers—orders of magnitude larger than any other modern scientist.

    This amount of correspondence testifies to Einstein’s centrality in the scientific life of Europe in the 1920s. He does become a nexus, at least in physics. And he is flooded by requests—everything from requests from indigent students up to requests from very famous people that he should endorse this or that appeal, contribute to this or that volume, or participate in this or that conference. He gets to be in great demand.

    He also gets a lot of inquiries from the general public about general relativity.

    Does he answer them?

    Yes, he tries to respond to every letter he gets. He was extremely disciplined. He spent quite a lot of time answering correspondence.

    Have any of your team’s discoveries been particularly exciting for you?

    I was excited when, a few years ago, we discovered some new letters from Croatia—from a Croatian physicist dating back to early in Einstein’s career. These were letters dating to 1911 and ’12, before Einstein finished general relativity. I’m always very pleased when we find material prior to 1915 or ’16 because Einstein’s path from special relativity to general relativity is one of the most exciting intellectual journeys. Whenever we uncover new material from that decade, it is quite significant, because we have so little material for the young Einstein compared to the older Einstein. Later, his correspondence grows exponentially.

    See the full article here.

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  • richardmitnick 6:01 pm on November 26, 2014 Permalink | Reply
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    From Caltech: “New Technique Could Harvest More of the Sun’s Energy” 

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    Caltech

    11/26/2014
    Jessica Stoller-Conrad

    As solar panels become less expensive and capable of generating more power, solar energy is becoming a more commercially viable alternative source of electricity. However, the photovoltaic cells now used to turn sunlight into electricity can only absorb and use a small fraction of that light, and that means a significant amount of solar energy goes untapped.

    A new technology created by researchers from Caltech, and described in a paper published online in the October 30 issue of Science Express, represents a first step toward harnessing that lost energy.

    m
    An ultra-sensitive needle measures the voltage that is generated while the nanospheres are illuminated.
    Credit: AMOLF/Tremani – Figure: Artist impression of the plasmo-electric effect.

    Sunlight is composed of many wavelengths of light. In a traditional solar panel, silicon atoms are struck by sunlight and the atoms’ outermost electrons absorb energy from some of these wavelengths of sunlight, causing the electrons to get excited. Once the excited electrons absorb enough energy to jump free from the silicon atoms, they can flow independently through the material to produce electricity. This is called the photovoltaic effect—a phenomenon that takes place in a solar panel’s photovoltaic cells.

    Although silicon-based photovoltaic cells can absorb light wavelengths that fall in the visible spectrum—light that is visible to the human eye—longer wavelengths such as infrared light pass through the silicon. These wavelengths of light pass right through the silicon and never get converted to electricity—and in the case of infrared, they are normally lost as unwanted heat.

    “The silicon absorbs only a certain fraction of the spectrum, and it’s transparent to the rest. If I put a photovoltaic module on my roof, the silicon absorbs that portion of the spectrum, and some of that light gets converted into power. But the rest of it ends up just heating up my roof,” says Harry A. Atwater, the Howard Hughes Professor of Applied Physics and Materials Science; director, Resnick Sustainability Institute, who led the study.

    Now, Atwater and his colleagues have found a way to absorb and make use of these infrared waves with a structure composed not of silicon, but entirely of metal.

    The new technique they’ve developed is based on a phenomenon observed in metallic structures known as plasmon resonance. Plasmons are coordinated waves, or ripples, of electrons that exist on the surfaces of metals at the point where the metal meets the air.

    While the plasmon resonances of metals are predetermined in nature, Atwater and his colleagues found that those resonances are capable of being tuned to other wavelengths when the metals are made into tiny nanostructures in the lab.

    “Normally in a metal like silver or copper or gold, the density of electrons in that metal is fixed; it’s just a property of the material,” Atwater says. “But in the lab, I can add electrons to the atoms of metal nanostructures and charge them up. And when I do that, the resonance frequency will change.”

    “We’ve demonstrated that these resonantly excited metal surfaces can produce a potential”—an effect very similar to rubbing a glass rod with a piece of fur: you deposit electrons on the glass rod. “You charge it up, or build up an electrostatic charge that can be discharged as a mild shock,” he says. “So similarly, exciting these metal nanostructures near their resonance charges up those metal structures, producing an electrostatic potential that you can measure.”

    This electrostatic potential is a first step in the creation of electricity, Atwater says. “If we can develop a way to produce a steady-state current, this could potentially be a power source. He envisions a solar cell using the plasmoelectric effect someday being used in tandem with photovoltaic cells to harness both visible and infrared light for the creation of electricity.

    Although such solar cells are still on the horizon, the new technique could even now be incorporated into new types of sensors that detect light based on the electrostatic potential.

    “Like all such inventions or discoveries, the path of this technology is unpredictable,” Atwater says. “But any time you can demonstrate a new effect to create a sensor for light, that finding has almost always yielded some kind of new product.”

    This work was published in a paper titled, Plasmoelectric Potentials in Metal Nanostructures. Other coauthors include first author Matthew T. Sheldon, a former postdoctoral scholar at Caltech; Ana M. Brown, an applied physics graduate student at Caltech; and Jorik van de Groep and Albert Polman from the FOM Institute AMOLF in Amsterdam. The study was funded by the Department of Energy, the Netherlands Organization for Scientific Research, and an NSF Graduate Research Fellowship.

    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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