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  • richardmitnick 3:10 pm on August 31, 2015 Permalink | Reply
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    From Caltech: “Seeing Quantum Motion” 

    Caltech Logo
    Caltech

    08/28/2015
    Jessica Stoller-Conrad

    1
    Credit: Chan Lei and Keith Schwab/Caltech

    Consider the pendulum of a grandfather clock. If you forget to wind it, you will eventually find the pendulum at rest, unmoving. However, this simple observation is only valid at the level of classical physics—the laws and principles that appear to explain the physics of relatively large objects at human scale. However, uantum mechanics, the underlying physical rules that govern the fundamental behavior of matter and light at the atomic scale, state that nothing can quite be completely at rest.

    For the first time, a team of Caltech researchers and collaborators has found a way to observe—and control—this quantum motion of an object that is large enough to see. Their results are published in the August 27 online issue of the journal Science.

    Researchers have known for years that in classical physics, physical objects indeed can be motionless. Drop a ball into a bowl, and it will roll back and forth a few times. Eventually, however, this motion will be overcome by other forces (such as gravity and friction), and the ball will come to a stop at the bottom of the bowl.

    “In the past couple of years, my group and a couple of other groups around the world have learned how to cool the motion of a small micrometer-scale object to produce this state at the bottom, or the quantum ground state,” says Keith Schwab, a Caltech professor of applied physics, who led the study. “But we know that even at the quantum ground state, at zero-temperature, very small amplitude fluctuations—or noise—remain.”

    Because this quantum motion, or noise, is theoretically an intrinsic part of the motion of all objects, Schwab and his colleagues designed a device that would allow them to observe this noise and then manipulate it.

    The micrometer-scale device consists of a flexible aluminum plate that sits atop a silicon substrate. The plate is coupled to a superconducting electrical circuit as the plate vibrates at a rate of 3.5 million times per second. According to the laws of classical mechanics, the vibrating structures eventually will come to a complete rest if cooled to the ground state.

    But that is not what Schwab and his colleagues observed when they actually cooled the spring to the ground state in their experiments. Instead, the residual energy—quantum noise—remained.

    “This energy is part of the quantum description of nature—you just can’t get it out,” says Schwab. “We all know quantum mechanics explains precisely why electrons behave weirdly. Here, we’re applying quantum physics to something that is relatively big, a device that you can see under an optical microscope, and we’re seeing the quantum effects in a trillion atoms instead of just one.”

    Because this noisy quantum motion is always present and cannot be removed, it places a fundamental limit on how precisely one can measure the position of an object.

    But that limit, Schwab and his colleagues discovered, is not insurmountable. The researchers and collaborators developed a technique to manipulate the inherent quantum noise and found that it is possible to reduce it periodically. Coauthors Aashish Clerk from McGill University and Florian Marquardt from the Max Planck Institute for the Science of Light proposed a novel method to control the quantum noise, which was expected to reduce it periodically. This technique was then implemented on a micron-scale mechanical device in Schwab’s low-temperature laboratory at Caltech.

    “There are two main variables that describe the noise or movement,” Schwab explains. “We showed that we can actually make the fluctuations of one of the variables smaller—at the expense of making the quantum fluctuations of the other variable larger. That is what’s called a quantum squeezed state; we squeezed the noise down in one place, but because of the squeezing, the noise has to squirt out in other places. But as long as those more noisy places aren’t where you’re obtaining a measurement, it doesn’t matter.”

    The ability to control quantum noise could one day be used to improve the precision of very sensitive measurements, such as those obtained by LIGO, the Laser Interferometry Gravitational-wave Observatory, a Caltech-and-MIT-led project searching for signs of gravitational waves, ripples in the fabric of space-time.

    LIGO
    Caltech Ligo

    “We’ve been thinking a lot about using these methods to detect gravitational waves from pulsars—incredibly dense stars that are the mass of our sun compressed into a 10 km radius and spin at 10 to 100 times a second,” Schwab says. “In the 1970s, Kip Thorne [Caltech’s Richard P. Feynman Professor of Theoretical Physics, Emeritus] and others wrote papers saying that these pulsars should be emitting gravity waves that are nearly perfectly periodic, so we’re thinking hard about how to use these techniques on a gram-scale object to reduce quantum noise in detectors, thus increasing the sensitivity to pick up on those gravity waves,” Schwab says.

    In order to do that, the current device would have to be scaled up. “Our work aims to detect quantum mechanics at bigger and bigger scales, and one day, our hope is that this will eventually start touching on something as big as gravitational waves,” he says.

    These results were published in an article titled, Quantum squeezing of motion in a mechanical resonator. In addition to Schwab, Clerk, and Marquardt, other coauthors include former graduate student Emma E. Wollman (PhD ’15); graduate students Chan U. Lei and Ari J. Weinstein; former postdoctoral scholar Junho Suh; and Andreas Kronwald of Friedrich-Alexander-Universität in Erlangen, Germany. The work was funded by the National Science Foundation (NSF), the Defense Advanced Research Projects Agency, and the Institute for Quantum Information and Matter, an NSF Physics Frontiers Center that also has support from 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 1:53 pm on August 31, 2015 Permalink | Reply
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    From Caltech: “New, Ultrathin Optical Devices Shape Light in Exotic Ways” 

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    Caltech

    08/31/2015
    Ker Than

    1
    Schematic drawing of generation and focusing of radially polarized light by a metasurface. Credit: Dr. Amir Arbabi/Faraon Lab/Caltech

    Caltech engineers have created flat devices capable of manipulating light in ways that are very difficult or impossible to achieve with conventional optical components.

    The new devices are not made of glass, but rather of silicon nanopillars that are precisely arranged into a honeycomb pattern to create a “metasurface” that can control the paths and properties of passing light waves.

    These metasurface devices, described in a paper published online on August 31, 2015, in the journal Nature Nanotechnology, could lead to ultracompact optical systems such as advanced microscopes, displays, sensors, and cameras that can be mass-produced using the same photolithography techniques used to manufacture computer microchips.

    “Currently, optical systems are made one component at a time, and the components are often manually assembled,” says Andrei Faraon (BS ’04), an assistant professor of applied physics and materials science, and the study’s principal investigator. “But this new technology is very similar to the one used to print semiconductor chips onto silicon wafers, so you could conceivably manufacture millions of systems such as microscopes or cameras at a time.”

    Seen under a scanning electron microscope [SEM], the new metasurfaces that the team created resemble a cut forest where only the stumps remain. Each silicon stump, or pillar, has an elliptical cross section, and by carefully varying the diameters of each pillar and rotating them around their axes, the scientists were able to simultaneously manipulate the phase and polarization of passing light. Light is an electromagnetic field, and the field of single-color, or monochromatic, light oscillates at all points in space with the same frequency but varying relative delays, or phases.

    Scanning electron microscope
    SEM

    Manipulating this relative delay, or phase, influences the degree to which a light ray bends, which in turn influences whether an image is in or out of focus.

    Polarization refers to the trajectory of the oscillations of the electromagnetic field at each point in space. Manipulating the polarization of light is essential for the operation of advanced microscopes, cameras, and displays; the control of polarization also enables simple gadgets such as 3-D glasses and polarized sunglasses.

    “Using our metasurfaces, we have complete control of the polarization and phase of light,” says study first author Amir Arbabi, a senior researcher at Caltech. “We can take any incoming light and shape its phase and polarization profiles arbitrarily and with very high efficiency.”

    While the same goal can be achieved using an arrangement of multiple conventional optical components such as glass lenses, prisms, spatial light modulators, polarizers, and wave plates, these many components lead to much bulkier systems. “If you think of a modern microscope, it has multiple components that have to be carefully assembled inside,” Faraon says. “But with our platform, we can actually make each of these optical components and stack them atop one another very easily using an automated process. Each component is just a millionth of a meter thick, or less than a hundredth of the thickness of a human hair. ”

    In addition to being compact, a metasurface device could manipulate light in novel ways that are very hard and sometimes impossible to do using current setups. For example, the Caltech team showed that one of their metasurfaces can project one image when illuminated by a horizontally polarized beam of light, and a different image when illuminated by a vertically polarized beam. “The two images will appear overlapped under illumination with light polarized at 45 degrees,” Faraon says.

    In another experiment, the team was able to use a metasurface to create a beam with radial polarization, that is, a beam whose polarization is pointing toward the beam axis. Such beams have doughnut-shaped intensity profiles and have applications in superresolution microscopy, laser cutting, and particle acceleration. “You generally would need a large optical setup, consisting of multiple components, to create this effect using conventional instruments,” Arbabi says. “With our setup, we can compress all of the optical components into one device and generate these beams with higher efficiency and more purity.”

    The team is currently working with industrial partners to create metasurfaces for use in commercial devices such as miniature cameras and spectrometers, but a limited number have already been produced for use in optical experiments by collaborating scientists in other disciplines.

    In addition, the Faraon lab current is investigating ways to combine different metasurfaces to create functioning optical systems and to correct for color distortions and other optical aberrations. “Like any optical system, you get distortions,” Faraon said. “That’s why expensive cameras have multiple lenses inside. Right now, we are experimenting with stacking different metasurfaces to correct for these aberrations and achieve novel functionalities.”

    The paper is entitled Dielectric metasurfaces for complete control of phase and polarization with sub wavelength spatial resolution and high transmission. In addition to Faraon and Arbabi, other Caltech coauthors include graduate student Yu Horie and Mahmood Bagheri, a microdevices engineer at JPL. The work was supported by the Caltech/JPL President’s and Director’s Fund and the Defense Advanced Research Projects Agency. Yu Horie was supported by the Department of Energy’s Energy Frontier Research Center program and a Japan Student Services Organization fellowship. The device nanofabrication was performed in the Kavli Nanoscience Institute at Caltech.

    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 7:15 pm on August 27, 2015 Permalink | Reply
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    From Caltech: “Caltech Chemists Solve Major Piece of Cellular Mystery” 

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    Caltech

    08/27/2015
    Kimm Fesenmaier

    Team determines the architecture of a second subcomplex of the nuclear pore complex [NPC]

    1
    Credit: Lance Hayashida/Caltech and the Hoelz Laboratory/Caltech

    2
    Credit: Hoelz Laboratory/Caltech

    Not just anything is allowed to enter the nucleus, the heart of eukaryotic cells where, among other things, genetic information is stored. A double membrane, called the nuclear envelope, serves as a wall, protecting the contents of the nucleus.

    3
    Human cell nucleus

    Any molecules trying to enter or exit the nucleus must do so via a cellular gatekeeper known as the nuclear pore complex (NPC), or pore, that exists within the envelope.

    How can the NPC be such an effective gatekeeper—preventing much from entering the nucleus while helping to shuttle certain molecules across the nuclear envelope? Scientists have been trying to figure that out for decades, at least in part because the NPC is targeted by a number of diseases, including some aggressive forms of leukemia and nervous system disorders such as a hereditary form of Lou Gehrig’s disease. Now a team led by André Hoelz, assistant professor of biochemistry at Caltech, has solved a crucial piece of the puzzle.

    In February of this year, Hoelz and his colleagues published a paper describing the atomic structure of the NPC’s coat nucleoporin complex, a subcomplex that forms what they now call the outer rings (see illustration). Building on that work, the team has now solved the architecture of the pore’s inner ring, a subcomplex that is central to the NPC’s ability to serve as a barrier and transport facilitator. In order to the determine that architecture, which determines how the ring’s proteins interact with each other, the biochemists built up the complex in a test tube and then systematically dissected it to understand the individual interactions between components. Then they validated that this is actually how it works in vivo, in a species of fungus.

    For more than a decade, other researchers have suggested that the inner ring is highly flexible and expands to allow large macromolecules to pass through. “People have proposed some complicated models to explain how this might happen,” says Hoelz. But now he and his colleagues have shown that these models are incorrect and that these dilations simply do not occur.

    “Using an interdisciplinary approach, we solved the architecture of this subcomplex and showed that it cannot change shape significantly,” says Hoelz. “It is a relatively rigid scaffold that is incorporated into the pore and basically just sits as a decoration, like pom-poms on a bicycle. It cannot dilate.”

    The new paper appears online ahead of print on August 27 in Science Express. The four co-lead authors on the paper are Caltech postdoctoral scholars Tobias Stuwe, Christopher J. Bley, and Karsten Thierbach, and graduate student Stefan Petrovic.

    Together, the inner and outer rings make up the symmetric core of the NPC, a structure that includes 21 different proteins. The symmetric core is so named because of its radial symmetry (the two remaining subcomplexes of the NPC are specific to either the side that faces the cell’s cytoplasm or the side that faces the nucleus and are therefore not symmetric). Having previously solved the structure of the coat nucleoporin complex and located it in the outer rings, the researchers knew that the remaining components that are not membrane anchored must make up the inner ring.

    They started solving the architecture by focusing on the channel nucleoporin complex, or channel, which lines the central transport channel and is made up of three proteins, accounting for about half of the inner ring. This complex produces filamentous structures that serve as docking sites for specific proteins that ferry molecules across the nuclear envelope.

    The biochemists employed bacteria to make the proteins associated with the inner ring in a test tube and mixed various combinations until they built the entire subcomplex. Once they had reconstituted the inner ring subcomplex, they were able to modify it to investigate how it is held together and which of its components are critical, and to determine how the channel is attached to the rest of the pore.

    Hoelz and his team found that the channel is attached at only one site. This means that it cannot stretch significantly because such shape changes require multiple attachment points. Hoelz notes that a new electron microscopy study of the NPC published in 2013 by Martin Beck’s group at the European Molecular Biology Laboratory (EMBL) in Heidelberg, Germany, indicated that the central channel is bigger than previously thought and wide enough to accommodate even the largest cargoes known to pass through the pore.

    When the researchers introduced mutations that effectively eliminated the channel’s single attachment, the complex could no longer be incorporated into the inner ring. After proving this in the test tube, they also showed this to be true in living cells.

    “This whole complex is a very complicated machine to assemble. The cool thing here is that nature has found an elegant way to wait until the very end of the assembly of the nuclear pore to incorporate the channel,” says Hoelz. “By incorporating the channel, you establish two things at once: you immediately form a barrier and you generate the ability for regulated transport to occur through the pore.” Prior to the channel’s incorporation, there is simply a hole through which macromolecules can freely pass.

    Next, Hoelz and his colleagues used X-ray crystallography to determine the structure of the channel nucleoporin subcomplex bound to the adaptor nucleoporin Nic96, which is its only nuclear pore attachment site. X-ray crystallography involves shining X-rays on a crystallized sample and analyzing the pattern of rays reflected off the atoms in the crystal. Because the NPC is a large and complex molecular machine that also has many moving parts, they used an engineered antibody to essentially “superglue” many copies of the complex into place to form a nicely ordered crystalline sample. Then they analyzed hundreds of samples using Caltech’s Molecular Observatory—a facility developed with support from the Gordon and Betty Moore Foundation that includes an automated X-ray beam line at the Stanford Synchrotron Radiation Laboratory that can be controlled remotely from Caltech—and the GM/CA beam line at the Advanced Photon Source at the Argonne National Laboratory. Eventually, they were able to determine the size, shape, and position of all the atoms of the channel nucleoporin subcomplex and its location within the full NPC.

    “The crystal structure nailed it,” Hoelz says. “There is no way that the channel is changing shape. All of that other work that, for more than 10 years, suggested it was dilating was wrong.”

    The researchers also solved a number of crystal structures from other parts of the NPC and determined how they interact with components of the inner ring. In doing so they demonstrated that one such interaction is critical for positioning the channel in the center of the inner ring. They found that exact positioning is needed for the proper export from the nucleus of mRNA and components of ribosomes, the cell’s protein-making complexes, rendering it critical in the flow of genetic information from DNA to mRNA to protein.

    Hoelz adds that now that the architectures of the inner and outer rings of the NPC are known, getting an atomic structure of the entire symmetric core is “a sprint to the summit.”

    “When I started at Caltech, I thought it might take another 10, 20 years to do this,” he says. “In the end, we have really only been working on this for four and a half years, and the thing is basically tackled. I want to emphasize that this kind of work is not doable everywhere. The people who worked on this are truly special, talented, and smart; and they worked day and night on this for years.”

    Ultimately, Hoelz says he would like to understand how the NPC works in great detail so that he might be able to generate therapies for diseases associated with the dysfunction of the complex. He also dreams of building up an entire pore in the test tube so that he can fully study it and understand what happens as it is modified in various ways. “Just as they did previously when I said that I wanted to solve the atomic structure of the nuclear pore, people will say that I’m crazy for trying to do this,” he says. “But if we don’t do it, it is likely that nobody else will.”

    The paper, “Architecture of the fungal nuclear pore inner ring complex,” had a number of additional Caltech authors: Sandra Schilbach (now of the Max Planck Institute of Biophysical Chemistry), Daniel J. Mayo, Thibaud Perriches, Emily J. Rundlet, Young E. Jeon, Leslie N. Collins, Ferdinand M. Huber, and Daniel H. Lin. Additional coauthors include Marcin Paduch, Akiko Koide, Vincent Lu, Shohei Koide, and Anthony A. Kossiakoff of the University of Chicago; and Jessica Fischer and Ed Hurt of Heidelberg University.

    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 2:28 pm on August 27, 2015 Permalink | Reply
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    From Caltech: “Artificial Leaf Harnesses Sunlight for Efficient Fuel Production” 

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    Caltech

    08/27/2015
    Jessica Stoller-Conrad

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    (From left to right): Chengxiang Xiang and Erik Verlage assemble a monolithically integrated III-V device, protected by a TiO2 stabilization layer, which performs unassisted solar water splitting with collection of hydrogen fuel and oxygen.
    Credit: Lance Hayashida/Caltech

    A highly efficient photoelectrochemical (PEC) device uses the power of the sun to split water into hydrogen and oxygen. The stand-alone prototype includes two chambers separated by a semi-permeable membrane that allows collection of both gas products.
    Credit: Lance Hayashida/Caltech
    3
    Illustration of an efficient, robust and integrated solar-driven prototype featuring protected photoelectrochemical assembly coupled with oxygen and hydrogen evolution reaction catalysts. [View full size]
    Credit: Image provided courtesy of Joint Center for Artificial Photosynthesis; artwork by Darius Siwek

    Generating and storing renewable energy, such as solar or wind power, is a key barrier to a clean-energy economy. When the Joint Center for Artificial Photosynthesis (JCAP) was established at Caltech and its partnering institutions in 2010, the U.S. Department of Energy (DOE) Energy Innovation Hub had one main goal: a cost-effective method of producing fuels using only sunlight, water, and carbon dioxide, mimicking the natural process of photosynthesis in plants and storing energy in the form of chemical fuels for use on demand. Over the past five years, researchers at JCAP have made major advances toward this goal, and they now report the development of the first complete, efficient, safe, integrated solar-driven system for splitting water to create hydrogen fuels.

    “This result was a stretch project milestone for the entire five years of JCAP as a whole, and not only have we achieved this goal, we also achieved it on time and on budget,” says Caltech’s Nate Lewis, George L. Argyros Professor and professor of chemistry, and the JCAP scientific director.

    The new solar fuel generation system, or artificial leaf, is described in the August 27 online issue of the journal Energy and Environmental Science. The work was done by researchers in the laboratories of Lewis and Harry Atwater, director of JCAP and Howard Hughes Professor of Applied Physics and Materials Science.

    “This accomplishment drew on the knowledge, insights and capabilities of JCAP, which illustrates what can be achieved in a Hub-scale effort by an integrated team,” Atwater says. “The device reported here grew out of a multi-year, large-scale effort to define the design and materials components needed for an integrated solar fuels generator.”

    The new system consists of three main components: two electrodes—one photoanode and one photocathode—and a membrane. The photoanode uses sunlight to oxidize water molecules, generating protons and electrons as well as oxygen gas. The photocathode recombines the protons and electrons to form hydrogen gas. A key part of the JCAP design is the plastic membrane, which keeps the oxygen and hydrogen gases separate. If the two gases are allowed to mix and are accidentally ignited, an explosion can occur; the membrane lets the hydrogen fuel be separately collected under pressure and safely pushed into a pipeline.

    Semiconductors such as silicon or gallium arsenide absorb light efficiently and are therefore used in solar panels. However, these materials also oxidize (or rust) on the surface when exposed to water, so cannot be used to directly generate fuel. A major advance that allowed the integrated system to be developed was previous work in Lewis’s laboratory, which showed that adding a nanometers-thick layer of titanium dioxide (TiO2)—a material found in white paint and many toothpastes and sunscreens—onto the electrodes could prevent them from corroding while still allowing light and electrons to pass through. The new complete solar fuel generation system developed by Lewis and colleagues uses such a 62.5-nanometer-thick TiO2 layer to effectively prevent corrosion and improve the stability of a gallium arsenide–based photoelectrode.

    Another key advance is the use of active, inexpensive catalysts for fuel production. The photoanode requires a catalyst to drive the essential water-splitting reaction. Rare and expensive metals such as platinum can serve as effective catalysts, but in its work the team discovered that it could create a much cheaper, active catalyst by adding a 2-nanometer-thick layer of nickel to the surface of the TiO2. This catalyst is among the most active known catalysts for splitting water molecules into oxygen, protons, and electrons and is a key to the high efficiency displayed by the device.

    The photoanode was grown onto a photocathode, which also contains a highly active, inexpensive, nickel-molybdenum catalyst, to create a fully integrated single material that serves as a complete solar-driven water-splitting system.

    A critical component that contributes to the efficiency and safety of the new system is the special plastic membrane that separates the gases and prevents the possibility of an explosion, while still allowing the ions to flow seamlessly to complete the electrical circuit in the cell. All of the components are stable under the same conditions and work together to produce a high-performance, fully integrated system. The demonstration system is approximately one square centimeter in area, converts 10 percent of the energy in sunlight into stored energy in the chemical fuel, and can operate for more than 40 hours continuously.

    “This new system shatters all of the combined safety, performance, and stability records for artificial leaf technology by factors of 5 to 10 or more ,” Lewis says.

    “Our work shows that it is indeed possible to produce fuels from sunlight safely and efficiently in an integrated system with inexpensive components,” Lewis adds, “Of course, we still have work to do to extend the lifetime of the system and to develop methods for cost-effectively manufacturing full systems, both of which are in progress.”

    Because the work assembled various components that were developed by multiple teams within JCAP, coauthor Chengxiang Xiang, who is co-leader of the JCAP prototyping and scale-up project, says that the successful end result was a collaborative effort. “JCAP’s research and development in device design, simulation, and materials discovery and integration all funneled into the demonstration of this new device,” Xiang says.

    These results are published in a paper titled A monolithically integrated, intrinsically safe, 10% efficient, solar-driven water-splitting system based on active, stable earth-abundant electrocatalysts in conjunction with tandem III-V light absorbers protected by amorphous TiO2 films. In addition to Lewis, Atwater, and Xiang, other Caltech coauthors include graduate student Erik Verlage, postdoctoral scholars Shu Hu and Ke Sun, material processing and integration research engineer Rui Liu, and JCAP mechanical engineer Ryan Jones. Funding was provided by the Office of Science at the U.S. Department of Energy, 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 8:27 am on August 21, 2015 Permalink | Reply
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    From Caltech: “Crush, the RoboSub, Places in International Competition” 

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    Caltech

    08/20/2015
    Lori Dajose

    1
    Crush, the RoboSub Credit: Caltech Robotics Team

    The Caltech Robotics Team—composed of 30 Caltech undergrads and recent alumni—placed fourth in the 18th Annual International RoboSub Competition, held July 20–26 in San Diego, California. The competition, hosted by the Association for Unmanned Vehicle Systems International (AUVSI) Foundation and cosponsored by the U.S. Office of Naval Research, challenges teams of student engineers to perform realistic missions with autonomous underwater vehicles (AUVs) in an underwater environment. Thirty-seven teams from across the globe competed in this year’s event.

    The challenge was to build a robotic submarine that could autonomously navigate an obstacle course, completing tasks such as driving through a gate, bumping into colored buoys, shooting torpedoes through holes, and dropping markers into designated bins. The only human involvement during the competition was the initial placement of the vehicle into the water.

    The Caltech team was divided into three groups, responsible for the mechanical, electrical, and software systems of the robot, which they named Crush. A fourth group managed the team’s fund-raising and outreach efforts. The mechanical team, led by Edward Fouad, a senior in mechanical engineering, was responsible for building grippers, a propulsion system, and a pressure hull to house the robot’s electronics. The autonomous capabilities of the robot were programmed from scratch by the software team, led by Kushal Agarwal, a junior in computer science. The electrical team, led by Torkom Pailevanian, a senior in electrical engineering, designed an inertial measurement unit consisting of gyroscopes and accelerometers that allow the robot to orient itself in 3-D space.

    Started in 1998, the Annual RoboSub Competition is designed to introduce young students into high-tech STEM fields such as maritime robotics. This year’s team from Caltech was led by Justin Koch—who graduated in June with his BS in mechanical engineering—and advised by Joel Burdick, the Richard L. and Dorothy M. Hayman Professor of Mechanical Engineering and Bioengineering.

    “Last year, as a first-year team, we placed seventh overall and were awarded Best New Entry,” says Koch. “I’m definitely very excited with how we did as only a second-year team!”

    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 4:03 pm on August 7, 2015 Permalink | Reply
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    From Caltech: “Caltech Announces Discovery in Fundamental Physics” 

    Caltech Logo
    Caltech

    08/07/2015
    Rod Pyle

    1
    One of the metallic samples studied, niobium diselenide, is seen here–the square in the center–as prepared for an X-ray diffraction experiment.
    Credit: University of Chicago/Argonne National Laboratory

    2
    This cutaway schematic shows the diamond anvil cell, a pressure vessel in which the experiments were conducted. The target material is situated between two diamonds, represented here in blue. For this study, a diamond anvil generated pressures to 100,000 times sea level.Credit: University of Chicago/Argonne National Laboratory

    When the transistor was invented in 1947 at Bell Labs, few could have foreseen the future impact of the device. This fundamental development in science and engineering was critical to the invention of handheld radios, led to modern computing, and enabled technologies such as the smartphone. This is one of the values of basic research.

    In a similar fashion, a branch of fundamental physics research, the study of so-called correlated electrons, focuses on interactions between the electrons in metals.

    The key to understanding these interactions and the unique properties they produce—information that could lead to the development of novel materials and technologies—is to experimentally verify their presence and physically probe the interactions at microscopic scales. To this end, Caltech’s Thomas F. Rosenbaum and colleagues at the University of Chicago and the Argonne National Laboratory recently used a synchrotron X-ray source to investigate the existence of instabilities in the arrangement of the electrons in metals as a function of both temperature and pressure, and to pinpoint, for the first time, how those instabilities arise. Rosenbaum, professor of physics and holder of the Sonja and William Davidow Presidential Chair, is the corresponding author on the paper that was published on July 27, 2015, in the journal Nature Physics.

    “We spent over 10 years developing the instrumentation to perform these studies,” says Yejun Feng of Argonne National Laboratory, a coauthor of the paper. “We now have a very unique capability that’s due to the long-term relationship between Dr. Rosenbaum and the facilities at the Argonne National Laboratory.”

    Within atoms, electrons are organized into orbital shells and subshells. Although they are often depicted as physical entities, orbitals actually represent probability distributions—regions of space where electrons have a certain likelihood of being found in a particular element at a particular energy. The characteristic electron configuration of a given element explains that element’s peculiar properties.

    The work in correlated electrons looks at a subset of electrons. Metals, as an example, have an unfilled outermost orbital and electrons are free to move from atom to atom. Thus, metals are good electrical conductors. When metal atoms are tightly packed into lattices (or crystals) these electrons mingle together into a “sea” of electrons. The metallic element mercury is liquid at room temperature, in part due to its electron configuration, and shows very little resistance to electric current due to its electron configuration. At 4 degrees above absolute zero (just barely above -460 degrees Fahrenheit), mercury’s electron arrangement and other properties create communal electrons that show no resistance to electric current, a state known as superconductivity.

    Mercury’s superconductivity and similar phenomena are due to the existence of many pairs of correlated electrons. In superconducting states, correlated electrons pair to form an elastic, collective state through an excitation in the crystal lattice known as a phonon (specifically, a periodic, collective excitation of the atoms). The electrons are then able to move cooperatively in the elastic state through a material without energy loss.

    Electrons in crystals can interact in many ways with the periodic structure of the underlying atoms. Sometimes the electrons modulate themselves periodically in space. The question then arises as to whether this “charge order” derives from the interactions of the electrons with the atoms, a theory first proposed more than 60 years ago, or solely from interactions among the sea of electrons themselves. This question was the focus of the Nature Physics study. Electrons also behave as microscopic magnets and can demonstrate “spin order,” which raises similar questions about the origin of the local magnetism.

    To see where the charge order arises, the researchers turned to the Advanced Photon Source at Argonne [APS].

    ANL APS
    ANL APS interior
    APS

    The Photon Source is a synchrotron (a relative of the cyclotron, commonly known as an “atom-smasher”). These machines generate intense X-ray beams that can be used for X-ray diffraction studies. In X-ray diffraction, the patterns of scattered X-rays are used to provide information about repeating structures with wavelengths at the atomic scale.

    In the experiment, the researchers used the X-ray beams to investigate charge-order effects in two metals, chromium and niobium diselenide, at pressures ranging from 0 (a vacuum) to 100 kilobar (100,000 times normal atmospheric pressure) and at temperatures ranging from 3 to 300 K (or -454 to 80 degrees Fahrenheit). Niobium diselenide was selected because it has a high degree of charge order, while chromium, in contrast, has a high degree of spin order.

    The researchers found that there is a simple correlation between pressure and how the communal electrons organize themselves within the crystal. Materials with completely different types of crystal structures all behave similarly. “These sorts of charge- and spin-order phenomena have been known for a long time, but their underlying mechanisms have not been understood until now,” says Rosenbaum.

    Paper coauthors Jasper van Wezel, formerly of Argonne National Laboratory and presently of the Institute for Theoretical Physics at the University of Amsterdam, and Peter Littlewood, a professor at the University of Chicago and the director of Argonne National Laboratory, helped to provide a new theoretical perspective to explain the experimental results.

    Rosenbaum and colleagues point out that there are no immediate practical applications of the results. However, Rosenbaum notes, “This work should have applicability to new materials as well as to the kind of interactions that are useful to create magnetic states that are often the antecedents of superconductors,” says Rosenbaum.

    “The attraction of this sort of research is to ask fundamental questions that are ubiquitous in nature,” says Rosenbaum. “I think it is very much a Caltech tradition to try to develop new tools that can interrogate materials in ways that illuminate the fundamental aspects of the problem.” He adds, “There is real power in being able to have general microscopic insights to develop the most powerful breakthroughs.”

    The coauthors on the paper, titled Itinerant density wave instabilities at classical and quantum critical points, are Yejun Feng and Peter Littlewood of the Argonne National Laboratory, Jasper van Wezel of the University of Amsterdam, Daniel M. Silevitch and Jiyang Wang of the University of Chicago, and Felix Flicker of the University of Bristol. Work performed at the Argonne National Laboratory was supported by the U.S. Department of Energy. Work performed at the University of Chicago was funded by the National Science Foundation. Additional support was received from the Netherlands Organization for Scientific Research

    See the full article here.

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  • richardmitnick 7:58 pm on August 5, 2015 Permalink | Reply
    Tags: , , Caltech   

    From Caltech: “Caltech Astronomers Unveil a Distant Protogalaxy Connected to the Cosmic Web” 

    Caltech Logo
    Caltech

    08/05/2015
    Kimm Fesenmaier

    1
    Using the Cosmic Web Imager at Palomar Observatory to study a system with two quasars 10 billion light years away, a team of astronomers led by Caltech has unveiled a giant swirling disk of gas—a protogalaxy, or galaxy in the making—being fed cool gas by a filament of the cosmic web.
    Credit: Caltech Academic Media Technologies

    A team of astronomers led by Caltech has discovered a giant swirling disk of gas 10 billion light-years away—a galaxy-in-the-making that is actively being fed cool primordial gas tracing back to the Big Bang. Using the Caltech-designed and -built Cosmic Web Imager (CWI) at Palomar Observatory, the researchers were able to image the protogalaxy and found that it is connected to a filament of the intergalactic medium, the cosmic web made of diffuse gas that crisscrosses between galaxies and extends throughout the universe.

    Caltech Palomar Cosmic Web Imager
    CWI

    Caltech Palomar Observatory
    Caltech Palomar Observatory interior
    Caltech Palomar Observatory

    The finding provides the strongest observational support yet for what is known as the cold-flow model of galaxy formation. That model holds that in the early universe, relatively cool gas funneled down from the cosmic web directly into galaxies, fueling rapid star formation.

    A paper describing the finding and how CWI made it possible currently appears online and will be published in the August 13 print issue of the journal Nature.

    “This is the first smoking-gun evidence for how galaxies form,” says Christopher Martin, professor of physics at Caltech, principal investigator on CWI, and lead author of the new paper. “Even as simulations and theoretical work have increasingly stressed the importance of cold flows, observational evidence of their role in galaxy formation has been lacking.”

    2
    Using the Cosmic Web Imager (CWI) at Palomar Observatory to study a system 10 billion light years away, a team of astronomers led by Caltech has unveiled a galaxy in the making being fed cool gas by a filament of the cosmic web. This picture combines a visible light image with data from CWI. A filament of the cosmic web (outlined here with parallel curved lines) can be seen funneling cold gas onto the protogalaxy (outlined with an ellipse). The CWI is an integral field spectrograph; the researchers used it to create a multiwavelength map showing the velocities with which gas in the system is moving with respect to the center of the system. The red side of the disk is rotating away from us, while the blue side is rotating toward us. Gas within the filament is moving at a constant velocity that matches the blue side of the rotating disk. Credit: Chris Martin/PCWI/Caltech

    The protogalactic disk the team has identified is about 400,000 light-years across—about four times larger in diameter than our Milky Way. It is situated in a system dominated by two quasars, the closest of which, UM287, is positioned so that its emission is beamed like a flashlight, helping to illuminate the cosmic web filament feeding gas into the spiraling protogalaxy.

    Last year, Sebastiano Cantalupo, then of UC Santa Cruz (now of ETH Zurich) and his colleagues published a paper, also in Nature, announcing the discovery of what they thought was a large filament next to UM287. The feature they observed was brighter than it should have been if indeed it was only a filament. It seemed that there must be something else there.

    In September 2014, Martin and his colleagues, including Cantalupo, decided to follow up with observations of the system with CWI. As an integral field spectrograph, CWI allowed the team to collect images around UM287 at hundreds of different wavelengths simultaneously, revealing details of the system’s composition, mass distribution, and velocity.

    3
    Using the Cosmic Web Imager at Palomar Observatory to study a system with two quasars 10 billion light years away, a team of astronomers led by Caltech has unveiled a giant swirling disk of gas — a protogalaxy, or galaxy in the making — being fed cool gas by a filament of the cosmic web. Credit: Chris Martin/PCWI/Caltech

    Martin and his colleagues focused on a range of wavelengths around an emission line in the ultraviolet known as the Lyman-alpha line. That line, a fingerprint of atomic hydrogen gas, is commonly used by astronomers as a tracer of primordial matter.

    The researchers collected a series of spectral images that combined to form a multiwavelength map of a patch of sky around the two quasars. This data delineated areas where gas is emitting in the Lyman-alpha line, and indicated the velocities with which this gas is moving with respect to the center of the system.

    “The images plainly show that there is a rotating disk—you can see that one side is moving closer to us and the other is moving away. And you can also see that there’s a filament that extends beyond the disk,” Martin says. Their measurements indicate that the disk is rotating at a rate of about 400 kilometers per second, somewhat faster than the Milky Way’s own rate of rotation.

    “The filament has a more or less constant velocity. It is basically funneling gas into the disk at a fixed rate,” says Matt Matuszewski (PhD ’12), an instrument scientist in Martin’s group and coauthor on the paper. “Once the gas merges with the disk inside the dark-matter halo, it is pulled around by the rotating gas and dark matter in the halo.” Dark matter is a form of matter that we cannot see that is believed to make up about 27 percent of the universe. Galaxies are thought to form within extended halos of dark matter.

    The new observations and measurements provide the first direct confirmation of the so-called cold-flow model of galaxy formation.

    Hotly debated since 2003, that model stands in contrast to the standard, older view of galaxy formation. The standard model said that when dark-matter halos collapse, they pull a great deal of normal matter in the form of gas along with them, heating it to extremely high temperatures. The gas then cools very slowly, providing a steady but slow supply of cold gas that can form stars in growing galaxies.

    That model seemed fine until 1996, when Chuck Steidel, Caltech’s Lee A. DuBridge Professor of Astronomy, discovered a distant population of galaxies producing stars at a very high rate only two billion years after the Big Bang. The standard model cannot provide the prodigious fuel supply for these rapidly forming galaxies.

    The cold-flow model provided a potential solution. Theorists suggested that relatively cool gas, delivered by filaments of the cosmic web, streams directly into protogalaxies. There, it can quickly condense to form stars. Simulations show that as the gas falls in, it contains tremendous amounts of angular momentum, or spin, and forms extended rotating disks.

    “That’s a direct prediction of the cold-flow model, and this is exactly what we see—an extended disk with lots of angular momentum that we can measure,” says Martin.

    Phil Hopkins, assistant professor of theoretical astrophysics at Caltech, who was not involved in the study, finds the new discovery “very compelling.”

    “As a proof that a protogalaxy connected to the cosmic web exists and that we can detect it, this is really exciting,” he says. “Of course, now you want to know a million things about what the gas falling into galaxies is actually doing, so I’m sure there is going to be more follow up.”

    Martin notes that the team has already identified two additional disks that appear to be receiving gas directly from filaments of the cosmic web in the same way.

    Additional Caltech authors on the paper, A giant protogalactic disk linked to the cosmic web, are principal research scientist Patrick Morrissey, research scientist James D. Neill, and instrument scientist Anna Moore from the Caltech Optical Observatories. J. Xavier Prochaska of UC Santa Cruz and former Caltech graduate student Daphne Chang, who is deceased, are also coauthors. The Cosmic Web Imager was funded by grants from the National Science Foundation and Caltech.

    See the full article here.

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  • richardmitnick 1:42 pm on July 29, 2015 Permalink | Reply
    Tags: , , Brown Dwarfs, Caltech   

    From Caltech: “”Failed Stars” Host Powerful Auroral Displays” 

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    Caltech

    07/29/2015
    Kimm Fesenmaier

    1
    Artist’s impression of an auroral display on a brown dwarf. Credit: Chuck Carter and Gregg Hallinan/Caltech

    Brown dwarfs are relatively cool, dim objects that are difficult to detect and hard to classify. They are too massive to be planets, yet possess some planetlike characteristics; they are too small to sustain hydrogen fusion reactions at their cores, a defining characteristic of stars, yet they have starlike attributes.

    By observing a brown dwarf 20 light-years away using both radio and optical telescopes, a team led by Gregg Hallinan, assistant professor of astronomy at Caltech, has found another feature that makes these so-called failed stars more like supersized planets—they host powerful auroras near their magnetic poles.

    The findings appear in the July 30 issue of the journal Nature.

    “We’re finding that brown dwarfs are not like small stars in terms of their magnetic activity; they’re like giant planets with hugely powerful auroras,” says Hallinan. “If you were able to stand on the surface of the brown dwarf we observed—something you could never do because of its extremely hot temperatures and crushing surface gravity—you would sometimes be treated to a fantastic light show courtesy of auroras hundreds of thousands of times more powerful than any detected in our solar system.”

    In the early 2000s, astronomers began finding that brown dwarfs emit radio waves. At first, everyone assumed that the brown dwarfs were creating the radio waves in basically the same way that stars do—through the action of an extremely hot atmosphere, or corona, heated by magnetic activity near the object’s surface. But brown dwarfs do not generate large flares and charged-particle emissions in the way that our sun and other stars do, so the radio emissions were surprising.

    While in graduate school, in 2006, Hallinan discovered that brown dwarfs can actually pulse at radio frequencies. “We see a similar pulsing phenomenon from planets in our solar system,” says Hallinan, “and that radio emission is actually due to auroras.” Since then he has wondered if the radio emissions seen on brown dwarfs might be caused by auroras.

    Auroral displays result when charged particles, carried by the stellar wind for example, manage to enter a planet’s magnetosphere, the region where such charged particles are influenced by the planet’s magnetic field. Once within the magnetosphere, those particles get accelerated along the planet’s magnetic field lines to the planet’s poles, where they collide with gas atoms in the atmosphere and produce the bright emissions associated with auroras.

    Following his hunch, Hallinan and his colleagues conducted an extensive observation campaign of a brown dwarf called LSRJ 1835+3259, using the National Radio Astronomy Observatory’s Very Large Array (VLA), the most powerful radio telescope in the world, as well as optical instruments that included Palomar’s Hale Telescope and the W. M. Keck Observatory’s telescopes.

    NRAO VLA
    NRAO/VLA

    Caltech Palomar 200 inch Hale Telescope
    Caltech Palomar 200 inch Hale Telescope interior
    Caltech Palomar Observatory

    Keck Observatory
    Keck Observatory Interior
    Keck Observatory

    Using the VLA they detected a bright pulse of radio waves that appeared as the brown dwarf rotated around. The object rotates every 2.84 hours, so the researchers were able to watch nearly three full rotations over the course of a single night.

    Next, the astronomers used the Hale Telescope to observe that the brown dwarf varied optically on the same period as the radio pulses. Focusing on one of the spectral lines associated with excited hydrogen—the h-alpha emission line—they found that the object’s brightness varied periodically.

    Finally, Hallinan and his colleagues used the Keck telescopes to measure precisely the brightness of the brown dwarf over time—no simple feat given that these objects are many thousands of times fainter than our own sun. Hallinan and his team were able to establish that this hydrogen emission is a signature of auroras near the surface of the brown dwarf.

    “As the electrons spiral down toward the atmosphere, they produce radio emissions, and then when they hit the atmosphere, they excite hydrogen in a process that occurs at Earth and other planets, albeit tens of thousands of times more intense,” explains Hallinan. “We now know that this kind of auroral behavior is extending all the way from planets up to brown dwarfs.”

    In the case of brown dwarfs, charged particles cannot be driven into their magnetosphere by a stellar wind, as there is no stellar wind to do so. Hallinan says that some other source, such as an orbiting planet moving through the brown dwarf’s magnetosphere, may be generating a current and producing the auroras. “But until we map the aurora accurately, we won’t be able to say where it’s coming from,” he says.

    He notes that brown dwarfs offer a convenient stepping stone to studying exoplanets, planets orbiting stars other than our own sun. “For the coolest brown dwarfs we’ve discovered, their atmosphere is pretty similar to what we would expect for many exoplanets, and you can actually look at a brown dwarf and study its atmosphere without having a star nearby that’s a factor of a million times brighter obscuring your observations,” says Hallinan.

    Just as he has used measurements of radio waves to determine the strength of magnetic fields around brown dwarfs, he hopes to use the low-frequency radio observations of the newly built Owens Valley Long Wavelength Array to measure the magnetic fields of exoplanets.

    Caltech Owens Radio Observatory
    Caltech Owens Valley Radio Observatory

    “That could be particularly interesting because whether or not a planet has a magnetic field may be an important factor in habitability,” he says. “I’m trying to build a picture of magnetic field strength and topology and the role that magnetic fields play as we go from stars to brown dwarfs and eventually right down into the planetary regime.”

    The work, Magnetospherically driven optical and radio aurorae at the end of the main sequence, was supported by funding from the National Science Foundation. Additional authors on the paper include Caltech senior postdoctoral scholar Stephen Bourke, Caltech graduate students Sebastian Pineda and Melodie Kao, Leon Harding of JPL, Stuart Littlefair of the University of Sheffield, Garret Cotter of the University of Oxford, Ray Butler of National University of Ireland, Galway, Aaron Golden of Yeshiva University, Gibor Basri of UC Berkeley, Gerry Doyle of Armagh Observatory, Svetlana Berdyugina of the Kiepenheuer Institute for Solar Physics, Alexey Kuznetsov of the Institute of Solar-Terrestrial Physics in Irkutsk, Russia, Michael Rupen of the National Radio Astronomy Observatory, and Antoaneta Antonova of Sofia University.

    See the full article here.

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  • richardmitnick 2:51 pm on July 20, 2015 Permalink | Reply
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    From Caltech: “Freezing a Bullet (+)” 

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    Caltech

    July 20, 2015
    Kimm Fesenmaier
    jnalick

    1
    Crystal structure of the assembly chaperone of ribosomal protein L4 (Acl4) that picks up a newly synthesized ribosomal protein when it emerges from the ribosome in the cytoplasm, protects it from the degradation machinery, and delivers it to the assembly site of new ribosomes in the nucleus. Credit: Ferdinand Huber/Caltech

    X-Ray Vision, an article in our Spring 2015 issue, examined the central role Caltech has played in developing a powerful technique for revealing the molecular machinery of life. In May, chemist André Hoeltz, who was featured in the article, published a new paper describing how he used the technique to reveal how protein-synthesizing cellular machines are built.

    Ribosomes are vital to the function of all living cells. Using the genetic information from RNA, these large molecular complexes build proteins by linking amino acids together in a specific order. Scientists have known for more than half a century that these cellular machines are themselves made up of about 80 different proteins, called ribosomal proteins, along with several RNA molecules and that these components are added in a particular sequence to construct new ribosomes, but no one has known the mechanism that controls that process.

    Now researchers from Caltech and Heidelberg University have combined their expertise to track a ribosomal protein in yeast all the way from its synthesis in the cytoplasm, the cellular compartment surrounding the nucleus of a cell, to its incorporation into a developing ribosome within the nucleus. In so doing, they have identified a new chaperone protein, known as Acl4, that ushers a specific ribosomal protein through the construction process and a new regulatory mechanism that likely occurs in all eukaryotic cells.

    The results, described in a paper that appears online in the journal Molecular Cell, also suggest an approach for making new antifungal agents.

    The work was completed in the labs of André Hoelz, assistant professor of chemistry at Caltech, and Ed Hurt, director of the Heidelberg University Biochemistry Center (BZH).

    “We now understand how this chaperone, Acl4, works with its ribosomal protein with great precision,” says Hoelz. “Seeing that is kind of like being able to freeze a bullet whizzing through the air and turn it around and analyze it in all dimensions to see exactly what it looks like.”

    That is because the entire ribosome assembly process—including the synthesis of new ribosomal proteins by ribosomes in the cytoplasm, the transfer of those proteins into the nucleus, their incorporation into a developing ribosome, and the completed ribosome’s export back out of the nucleus into the cytoplasm—happens in the tens of minutes timescale. So quickly that more than a million ribosomes are produced per day in mammalian cells to allow for turnover and cell division. Therefore, being able to follow a ribosomal protein through that process is not a simple task.

    Hurt and his team in Germany have developed a new technique to capture the state of a ribosomal protein shortly after it is synthesized. When they “stopped” this particular flying bullet, an important ribosomal protein known as L4, they found that its was bound to Acl4.

    Hoelz’s group at Caltech then used X-ray crystallography to obtain an atomic snapshot of Acl4 and further biochemical interaction studies to establish how Acl4 recognizes and protects L4. They found that Acl4 attaches to L4 (having a high affinity for only that ribosomal protein) as it emerges from the ribosome that produced it, akin to a hand gripping a baseball. Thereby the chaperone ensures that the ribosomal protein is protected from machinery in the cell that would otherwise destroy it and ushers the L4 molecule through the sole gateway between the nucleus and cytoplasm, called the nuclear pore complex, to the site in the nucleus where new ribosomes are constructed.

    “The ribosomal protein together with its chaperone basically travel through the nucleus and screen their surroundings until they find an assembling ribosome that is at exactly the right stage for the ribosomal protein to be incorporated,” explains Ferdinand Huber, a graduate student in Hoelz’s group and one of the first authors on the paper. “Once found, the chaperone lets the ribosomal protein go and gets recycled to go pick up another protein.”

    The researchers say that Acl4 is just one example from a whole family of chaperone proteins that likely work in this same fashion.

    Hoelz adds that if this process does not work properly, ribosomes and proteins cannot be made. Some diseases (including aggressive leukemia subtypes) are associated with malfunctions in this process.

    “It is likely that human cells also contain a dedicated assembly chaperone for L4. However, we are certain that it has a distinct atomic structure, which might allow us to develop new antifungal agents,” Hoelz says. “By preventing the chaperone from interacting with its partner, you could keep the cell from making new ribosomes. You could potentially weaken the organism to the point where the immune system could then clear the infection. This is a completely new approach.”

    Co-first authors on the paper, Coordinated Ribosomal L4 Protein Assembly into the Pre-Ribosome Is Regulated by Its Eukaryote-Specific Extension, are Huber and Philipp Stelter of Heidelberg University. Additional authors include Ruth Kunze and Dirk Flemming also from Heidelberg University. The work was supported by the Boehringer Ingelheim Fonds, the V Foundation for Cancer Research, the Edward Mallinckrodt, Jr. Foundation, the Sidney Kimmel Foundation for Cancer Research, and the German Research Foundation (DFG).

    See the full article here.

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  • richardmitnick 10:47 am on June 4, 2015 Permalink | Reply
    Tags: , , Caltech, CARMA Array,   

    From Caltech: “Celebrating 11 Years of CARMA Discoveries” 

    Caltech Logo
    Caltech

    06/03/2015
    Ker Than

    CARMA Array
    CARMA Array

    For more than a decade, large, moveable telescopes tucked away on a remote, high-altitude site in the Inyo Mountains, about 250 miles northeast of Los Angeles, have worked together to paint a picture of the universe through radio-wave observations.

    Known as the Combined Array for Research in Millimeter-wave Astronomy, or CARMA, the telescopes formed one of the most powerful millimeter interferometers in the world. CARMA was created in 2004 through the merger of the Owens Valley Radio Observatory (OVRO) Millimeter Array and the Berkeley Illinois Maryland Association (BIMA) Array and initially consisted of 15 telescopes. In 2008, the University of Chicago joined CARMA, increasing the telescope count to 23.

    2
    An artist’s depiction of a gamma ray burst, the most powerful explosive event in the universe. CARMA detected the millimeter-wavelength emission from the afterglow of the gamma ray burst 130427A only 18 hours after it first exploded on April 27, 2013. The CARMA observations revealed a surprise: in addition to the forward moving shock, CARMA showed the presence of a backward moving shock, or “reverse” shock, that had long been predicted, but never conclusively observed until now. Credit: Gemini Observatory/AURA, artwork by Lynette Cook

    CARMA’s higher elevation, improved electronics, and greater number of connected antennae enabled more precise observations of radio emission from molecules and cold dust across the universe, leading to ground-breaking studies that encompass a range of cosmic objects and phenomena—including stellar birth, early planet formation, supermassive black holes, galaxies, galaxy mergers, and sudden, unexpected events such as gamma-ray bursts and supernova explosions.

    “Over its lifetime, it has moved well beyond its initial goals both scientifically and technically,” says Anneila Sargent (MS ’67, PhD ’78, both degrees in astronomy), the Ira S. Bowen Professor of Astronomy at Caltech and the first director of CARMA.

    On April 3, CARMA probed the skies for the last time. The project ceased operations and its telescopes will be repurposed and integrated into other survey projects.

    Here is a look back at some of CARMA’s most significant discoveries and contributions to the field of astronomy.

    4
    These CARMA images highlight the range of morphologies observed in circumstellar disks, which may indicate that the disks are in different stages in the planet formation process, or that they are evolving along distinct pathways. The bottom row highlights the disk around the star LkCa 15, where CARMA detected a 40 AU diameter inner hole. The two-color Keck image (bottom right) reveals an infrared source along the inner edge of this hole. The infrared luminosity is consistent with a 6M Jupiter planet, which may have cleared the hole.
    Credit: CARMA

    Planet Formation

    Newly formed stars are surrounded by a rotating disk of gas and dust, known as a circumstellar disk. These disks provide the building materials for planetary systems like our own solar system, and can contain important clues about the planet formation process.

    During its operation, CARMA imaged disks around dozens of young stars such as RY Tau and DG Tau. The observations revealed that circumstellar disks often are larger in size than our solar system and contain enough material to form Jupiter-size planets. Interestingly, these disks exhibit a variety of morphologies, and scientists think the different shapes reflect different stages or pathways of the planet formation process.

    CARMA also helped gather evidence that supported planet formation theories by capturing some of the first images of gaps in circumstellar disks. According to conventional wisdom, planets can form in disks when stars are as young as half a million years old. Computer models show that if these so-called protoplanets are the size of Jupiter or larger, they should carve out gaps or holes in the rings through gravitational interactions with the disk material. In 2012, the team of OVRO executive director John Carpenter reported using CARMA to observe one such gap in the disk surrounding the young star LkCa 15. Observations by the Keck Observatory in Hawaii revealed an infrared source along the inner edge of the gap that was consistent with a planet that has six times the mass of Jupiter.

    Keck Observatory
    Keck

    “Until ALMA”—the Atacama Large Millimeter/submillimeter Array in Chile, a billion-dollar international collaboration involving the United States, Europe, and Japan—”came along, CARMA produced the highest-resolution images of circumstellar disks at millimeter wavelengths,” says Carpenter.

    ALMA Array
    ALMA

    5
    A color image of the Whirlpool galaxy M51 from the Hubble Space Telescope (HST). A three composite of images taken at wavelengths of 4350 Angstroms (blue), 5550 Angstroms (green), and 6580 Angstroms (red). Bright regions in the red color are the regions of recent massive star formation, where ultraviolet photons from the massive stars ionize the surrounding gas which radiates the hydrogen recombination line emission. Dark lanes run along spiral arms, indicating the location where the dense interstellar medium is abundant.
    Credit: Jin Koda

    Star Formation

    Stars form in “clouds” of gas, consisting primarily of molecular hydrogen, that contain as much as a million times the mass of the sun. “We do not understand yet how the diffuse molecular gas distributed over large scales flows to the small dense regions that ultimately form stars,” Carpenter says.

    Magnetic fields may play a key role in the star formation process, but obtaining observations of these fields, especially on small scales, is challenging. Using CARMA, astronomers were able to chart the direction of the magnetic field in the dense material that surrounds newly formed protostars by mapping the polarized thermal radiation from dust grains in molecular clouds. A CARMA survey of the polarized dust emission from 29 sources showed that magnetic fields in the dense gas are randomly aligned with outflowing gas entrained by jets from the protostars.

    If the outflows emerge along the rotation axes of circumstellar disks, as has been observed in a few cases, the results suggest that, contrary to theoretical expectations, the circumstellar disks are not aligned with the fields in the dense gas from which they formed. “We don’t know the punch line—are magnetic fields critical in the star formation process or not?—because, as always, the observations just raise more questions,” Carpenter admits. “But the CARMA observations are pointing the direction for further observations with ALMA.”

    6
    CARMA was used to image molecular gas in the nearby Andromeda galaxy. All stars form in dense clouds of molecular gas and thus to understand star formation it is important to analyze the properties of molecular clouds.
    Credit: Andreas Schruba

    Molecular gas in galaxies

    The molecular gas in galaxies is the raw material for star formation. “Being able to study how much gas there is in a galaxy, how it’s converted to stars, and at what rate is very important for understanding how galaxies evolve over time,” Carpenter says.

    By resolving the molecular gas reservoirs in local galaxies and measuring the mass of gas in distant galaxies that existed when the cosmos was a fraction of its current age, CARMA made fundamental contributions to understanding the processes that shape the observable universe.

    For example, CARMA revealed the evolution, in the spiral galaxy M51, of giant molecular clouds (GMCs) driven by large-scale galactic structure and dynamics. CARMA was used to show that giant molecular clouds grow through coalescence and then break up into smaller clouds that may again come together in the future. Furthermore, the process can occur multiple times over a cloud’s lifetime. This new picture of molecular cloud evolution is more complex than previous scenarios, which treated the clouds as discrete objects that dissolved back into the atomic interstellar medium after a certain period of time. “CARMA’s imaging capability showed the full cycle of GMCs’ dynamical evolution for the first time,” Carpenter says.

    The Milky Way’s black hole

    CARMA worked as a standalone array, but it was also able to function as part of very-long-baseline interferometry (VLBI), in which astronomical radio signals are gathered from multiple radio telescopes on Earth to create higher-resolution images than is possible with single telescopes working alone.

    In this fashion, CARMA has been linked together with the Submillimeter Telescope in Arizona and the James Clerk Maxwell Telescope and Submillimeter Array in Hawaii to paint one of the most detailed pictures to date of the monstrous black hole at the heart of our Milky Way galaxy. The combined observations achieved an angular resolution of 40 microarcseconds—the equivalent of seeing a tennis ball on the moon.

    “If you just used CARMA alone, then the best resolution you would get is 0.15 arcseconds. So VLBI improved the resolution by a factor of 3,750,” Carpenter says.

    Astronomers have used the VLBI technique to successfully detect radio signals emitted from gas orbiting just outside of this supermassive black hole’s event horizon, the radius around the black hole where gravity is so strong that even light cannot escape. “These observations measured the size of the emitting region around the black hole and placed constraints on the accretion disk that is feeding the black hole,” he explains.

    In other work, VLBI observations showed that the black hole at the center of M87, a giant elliptical galaxy, is spinning.

    Transients

    CARMA also played an important role in following up “transients,” objects that unexpectedly burst into existence and then dim and fade equally rapidly (on an astronomical timescale), over periods from seconds to years. Some transients can be attributed to powerful cosmic explosions such as gamma-ray bursts (GRBs) or supernovas, but the mechanisms by which they originate remain unexplained.

    “By looking at transients at different wavelengths—and, in particular, looking at them soon after they are discovered—we can understand the progenitors that are causing these bursts,” says Carpenter, who notes that CARMA led the field in observations of these events at millimeter wavelengths. Indeed, on April 27, 2013, CARMA detected the millimeter-wavelength emission from the afterglow of GRB 130427A only 18 hours after it first exploded.

    7
    GRB 130427A Before and after in 100+ MeV light

    The CARMA observations revealed a surprise: in addition to the forward-moving shock, there was one moving backward. This “reverse” shock had long been predicted, but never conclusively observed.

    Getting data on such unpredictable transient events is difficult at many observatories, because of logistics and the complexity of scheduling. “Targets of opportunity require flexibility on the part of the organization to respond to an event when it happens,” says Sterl Phinney (BS ’80, astronomy), professor of theoretical astrophysics and executive officer for astronomy and astrophysics at Caltech. “CARMA was excellent for this purpose, because it was so nimble.”

    7
    Multi-wavelength view of the redshift z=0.2 cluster MS0735+7421. Left to right: CARMA observations of the SZ effect, X-ray data from Chandra, radio data from the VLA, and a three-color composite of the three. The SZ image reveals a large-scale distortion of the intra-cluster medium coincident with X-ray cavities produced by a massive AGN outflow, an example of the wide dynamic-range, multi-wavelength cluster imaging enabled by CARMA. Credit: Erik Leitch (University of Chicago, Owens Valley Radio Observatory)

    Galaxy clusters

    Galaxy clusters are the largest gravitationally bound objects in the universe. CARMA studied galaxy clusters by taking advantage of a phenomenon known as the Sunyaev-Zel’dovich (SZ) effect. The SZ effect results when primordial radiation left over from the Big Bang, known as the cosmic microwave background (CMB), is scattered to higher energies after interacting with the hot ionized gas that permeates galaxy clusters. Using CARMA, astronomers recently confirmed a galaxy cluster candidate at redshifts of 1.75 and 1.9, making them the two most distant clusters for which an SZ effect has been measured.

    “CARMA can detect the distortion in the CMB spectrum,” Carpenter says. “We’ve observed over 100 clusters at very good resolution. These data have been very important to calibrating the relation between the SZ signal and the cluster mass, probing the structure of clusters, and helping discover the most distant clusters known in the universe.”

    Training the next generation

    In addition to its many scientific contributions, CARMA also served as an important teaching facility for the next generation of astronomers. About 300 graduate students and postdoctoral researchers have cut their teeth on interferometry astronomy at CARMA over the years. “They were able to get hands-on experience in millimeter-wave astronomy at the observatory, something that is becoming more and more rare these days,” Sargent says.

    Tom Soifer (BS ’68, physics), professor of physics and Kent and Joyce Kresa Leadership Chair of the Division of Physics, Mathematics and Astronomy, notes that many of those trainees now hold prestigious positions at the National Radio Astronomy Observatory (NRAO) or are professors at universities across the country, where they educate future scientists and engineers and help with the North American ALMA effort. “The United States is currently part of a tripartite international collaboration that operates ALMA. Most of the North American ALMA team trained either at CARMA or the Caltech OVRO Millimeter Array, CARMA’s precursor,” he says.

    Looking ahead

    Following CARMA’s shutdown, the Cedar Flats sites will be restored to prior conditions, and the telescopes will be moved to OVRO. Although the astronomers closest to the observatory find the closure disappointing, Phinney takes a broader view, seeing the shutdown as part of the steady march of progress in astronomy. “CARMA was the cutting edge of high-frequency astronomy for the past decade. Now that mantle has passed to the global facility called ALMA, and Caltech will take on new frontiers.”

    Indeed, Caltech continues to push the technological frontier of astronomy through other projects. For example, Caltech Assistant Professor of Astronomy Greg Hallinan is leading the effort to build a Long Wavelength Array (LWA) station at OVRO that will instantaneously image the entire viewable sky every few seconds at low-frequency wavelengths to search for radio transients.

    The success of CARMA and OVRO, Soifer says, gives him confidence that the LWA will also be successful. “We have a tremendously capable group of scientists and engineers. If anybody can make this challenging enterprise work, they can.”

    See the full article here.

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