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  • richardmitnick 7:03 am on February 25, 2014 Permalink | Reply
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    From Berkeley Lab: “On the Road to Mottronics…” 


    Berkeley Lab

    Researchers at the Advanced Light Source Find Key to Controlling the Electronic and Magnetic Properties of Mott Thin Films

    February 24, 2014
    Lynn Yarris (510) 486-5375 lcyarris@lbl.gov

    Mottronics” is a term seemingly destined to become familiar to aficionados of electronic gadgets. Named for the Nobel laureate Nevill Francis Mott, Mottronics involve materials – mostly metal oxides – that can be induced to transition between electrically conductive and insulating phases. If these phase transitions can be controlled, Mott materials hold great promise for future transistors and memories that feature higher energy efficiencies and faster switching speeds than today’s devices. A team of researchers working at Berkeley Lab’s Advanced Light Source (ALS) have demonstrated the conducting/insulating phases of ultra-thin films of Mott materials can be controlled by applying an epitaxial strain to the crystal lattice.

    balls
    Epitaxial mismatches in the lattices of nickelate ultra-thin films can be used to tune the energetic landscape of Mott materials and thereby control conductor/insulator transitions. No image credit.

    “Our work shows how an epitaxial mismatch in the lattice can be used as a knot to tune the energetic landscape of Mott materials and thereby control conductor/insulator transitions,” says Jian Liu, a post-doctoral scholar now with Berkeley Lab’s Materials Sciences Division, who is the lead author on a paper describing this work in the journal Nature Communications. “Through epitaxial strain, we forced nickelate films containing only a few atomic layers into different phases with dramatically different electronic and magnetic properties. While some of these phases are not obtainable in conventional ways, we were able to produce them in a form that is ready for device development.”

    The Nature Communications paper is titled Heterointerface engineered electronic and magnetic phases of NdNiO3 thin films. The corresponding author is Jak Chakhalian, a professor of physics at the University of Arkansas. Co-authors are Mehdi Kargarian, Mikhail Kareev, Ben Gray, Phil Ryan, Alejandro Cruz, Nadeem Tahir, Yi-De Chuang, Jinghua Guo, James Rondinelli, John Freeland and Gregory Fiete.

    two
    Jinghua Guo (left) and Yi-De Chuang at Beamline 8.0.1 of the Advanced Light Source were part of a team that discovered a key to controlling the electronic and magnetic properties of Mott materials. (Photo by Roy Kaltschmidt)

    Nickel-based rare-earth perovskite oxides, or “nickelates,” are considered to be an ideal model for the study of Mott materials because they display strongly correlated electron systems that give rise to unique electronic and magnetic properties. Liu and his co-authors studied thin films of neodymium nickel oxide using ALS beamline 8.0.1, a high flux undulator beamline that produces x-ray beams optimized for the study of nanoscale materials and strongly correlated physics.

    “ALS beamline 8.0.1 provides the high photon flux and energy range that are critical when dealing with nanoscale samples,” Liu says. “The state-of-the-art Resonant X-ray Scattering endstation has a high-speed, high-sensitivity CCD camera that makes it feasible to find and track diffraction peaks off a thin film that was only six nanometers thick.”

    The transition between the conducting and insulating phases in nickelates is determined by various microscopic interactions, some of which favor the conducting phase, some which favor the insulating phase. The energetic balance of these interactions determines how easily electricity is conducted by electrons moving between the nickel and oxygen ions. By applying enough epitaxial strain to alter the space between these ions, Liu and his colleagues were able to tune this energetic balance and control the conducting/insulating transition. In addition, they found strain could also be used to control the nickelate’s magnetic properties, again by exploiting the lattice mismatch.

    “Magnetism is another hallmark of Mott materials that often goes hand-in-hand with the insulating state and is used to distinguish Mott insulators,” says Liu. “The challenge is that most Mott insulators, including nickelates, are antiferromagnets that macroscopically behave as non-magnetic materials. “At ALS beamline 8.0.1, we were able to directly track the magnetic evolution of our thin films while tuning the metal-to-insulator transition. Our findings give us a better understanding of the physics behind the magnetic properties of these nickelate films and point to potential applications for this magnetism in novel Mottronics devices.”

    This research was primarily supported the U.S. Department of Energy’s Office of Science.

    See the full article here.

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  • richardmitnick 7:25 pm on February 21, 2014 Permalink | Reply
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    From Berkeley Lab: “Tracking Catalytic Reactions in Microreactors” 


    Berkeley Lab

    See the full article here.

    February 21, 2014

    Infrared Technique at Berkeley Lab’s Advanced Light Source Could Help Improve Flow Reactor Chemistry for Pharmaceuticals and Other Products

    Lynn Yarris (510) 486-5375 lcyarris@lbl.gov

    A pathway to more effective and efficient synthesis of pharmaceutical drugs and other flow reactor chemical products has been opened by a study in which for the first time the catalytic reactivity inside a microreactor was mapped in high resolution from start-to-finish. The results not only provided a better understanding of the chemistry behind the catalytic reactions, they also revealed opportunities for optimization, which resulted in better catalytic performances. The study was conducted by a team of scientists with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley.

    Working at Berkeley Lab’s Advanced Light Source (ALS), the team, which was led by chemists Dean Toste and Gabor Somorjai, both of whom hold joint appointments with Berkeley Lab and UC Berkeley, used tightly focused beams of infrared and x-ray light to track the evolution of a catalytic reaction with a spatial resolution of 15 microns.

    graph
    Infrared microspectroscopy scans can track the formation of different chemical products as reactants flow through a microreactor.

    “The formation of different chemical products during the reactions was analyzed using in situ infrared micro-spectroscopy, while the state of the catalyst along the flow reactor was determined using in situ x-ray absorption microspectroscopy,” says Toste, a faculty scientist with Berkeley Lab’s Chemical Sciences Division. “Our results show that using infrared microspectroscopy to monitor the evolution of reactants into a desired product could be an invaluable tool for optimizing pharmaceutical-related synthetic processes that take place in flow reactors.”

    two
    Dean Toste (left) and Elad Gross led a team that developed a technique which allows the catalytic reactivity inside a microreactor to be mapped in high resolution from start-to-finish. (Photo by Roy Kaltschmidt)

    Toste and Somorjai are the corresponding authors of a paper in the Journal of the American Chemical Society (JACS) titled In-situ IR and X-ray high spatial-resolution microspectroscopy measurements of multistep organic transformation in flow microreactor catalyzed by Au nanoclusters. Elad Gross, a post-doctoral scholar with the corresponding authors, is the lead author. Other co-authors are Xing-Zhong Shu, Selim Alayoglu, Hans Bechtel and Michael Martin.

    Catalysts – substances that speed up the rates of chemical reactions without themselves being chemically changed – are used to initiate virtually every manufacturing process that involves chemistry. There are two basic modes of catalytic reactors – batch, in which a final chemical product is produced over a series of separate stages; and flow, in which chemical reactions run in a continuously flowing stream to yield a final product. With the implementation of microreactors, the pharmaceutical industry aims to make the switch from batch mode to flow mode, as flow reactors provide a highly recyclable, scalable and efficient setup that enhances the sustainability and performance of catalysts. However, the synthesis of pharmaceutical drugs is a multiphase, complex process that needs to be carefully monitored. Until now, there has been no capability to follow the multistep production process of pharmaceutical drugs in flow reactors without perturbing the flow reaction.

    “Our method allows us to watch an entire catalytic movie, from reactants into products formation, instead of only snapshots of the catalytic process,” says Gross. “In most cases before, chemists had to extrapolate information on the reaction process based on analysis of the final product. With our technique, we don’t have to guess what happened in the first scene based on what we saw in the final scene, since now we’re able to directly watch a high-resolution movie of the entire process.”

    For this study, Gross and his colleagues used a heterogeneous catalyst of gold nanoclusters loaded onto a silica support to produce dihydropyran, an organic compound whose formation involves multiple reactant steps. Each of these reactants shows a distinguishable infrared signature, allowing their evolution into the final product to be precisely monitored with an infrared beam. The infrared microspectroscopy was performed at ALS beamline 1.4.

    “ALS beamline 1.4 provides a bright infrared beam with a diameter of less than 10 micrometers,” Gross says. “The small diameter of the beam enabled us to draw a map of the flow reactor with high spatial resolution of up to 15 micrometers. Without this high resolution imaging, we would not be able to track and understand key processes in the catalytic reaction.”

    map
    A combination of in situ infrared micro-spectroscopy and in situ x-ray absorption microspectroscopy allows catalytic reactivity inside a microreactor to be mapped in high resolution from start-to-finish.

    In following the reaction kinetics step-by-step, the Berkeley researchers discovered that the catalytic reaction they were observing is completed within the first five-percent of the flow reactor’s volume, which meant that the remaining 95-percent of the reactor, though packed with catalyst did not contribute to the catalytic process.

    “Based on this result, we were able to minimize the volume of the flow reactor and the amount of catalyst by an order of magnitude without deteriorating the catalytic reactivity,” Gross says.

    While the infrared microspectroscopy technique employed in this study allowed one-dimensional mapping of a catalytic reaction along the path of the flow reactor, the actual flow reactor is three-dimensional. Gross and Toste along with Michael Martin and Hans Bechtel, beam-scientists at the ALS infrared beamline, are now exploring techniques that would permit two- and three-dimensional mapping of catalytic reactions.

    “Multidimensional imaging will give us the ability to know where exactly inside the volume of the flow reactor the catalytic reaction takes place,” Gross says. “This will provide us advanced tools for better understanding and optimization of the catalytic reaction.”

    This research was supported by the DOE Office of Science.

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  • richardmitnick 6:19 pm on February 6, 2014 Permalink | Reply
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    From Berkeley Lab: “New Insight into an Emerging Genome-Editing Tool” 


    Berkeley Lab

    Berkeley Researchers Show Expanded Role for Guide RNA in Cas9 Interactions with DNA

    February 06, 2014
    Lynn Yarris (510) 486-5375 lcyarris@lbl.gov

    The potential is there for bacteria and other microbes to be genetically engineered to perform a cornucopia of valuable goods and services, from the production of safer, more effective medicines and clean, green, sustainable fuels, to the clean-up and restoration of our air, water and land. Cells from eukaryotic organisms can also be modified for research or to fight disease. To achieve these and other worthy goals, the ability to precisely edit the instructions contained within a target’s genome is a must. A powerful new tool for genome editing and gene regulation has emerged in the form of a family of enzymes known as Cas9, which plays a critical role in the bacterial immune system. Cas9 should become an even more valuable tool with the creation of the first detailed picture of its three-dimensional shape by researchers with the Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley.

    dna
    The crystal structure of SpyCas9 features a nuclease domain lobe (red) and an alpha-helical lobe (gray) each with a nucleic acid binding cleft that becomes functionalized when Cas9 binds to guide RNA.

    binding
    Upon binding with guide RNA, the two structural lobes of Cas9 reorient so that the two nucleic acid binding clefts face each other, forming a central channel that interfaces with target DNA.

    Biochemist Jennifer Doudna and biophysicist Eva Nogales, both of whom hold appointments with Berkeley Lab, UC Berkeley, and the Howard Hughes Medical Institute (HHMI), led an international collaboration that used x-ray crystallography to produce 2.6 and 2.2 angstrom (Å) resolution crystal structure images of two major types of Cas9 enzymes. The collaboration then used single-particle electron microscopy to reveal how Cas9 partners with its guide RNA to interact with target DNA. The results point the way to the rational design of new and improved versions of Cas9 enzymes for basic research and genetic engineering.

    “The combination of x-ray protein crystallography and electron microscopy single-particle analysis showed us something that was not anticipated,” says Nogales. “The Cas9 protein, on its own, exists in an inactive state, but upon binding to the guide RNA, the Cas9 protein undergoes a radical change in its three-dimensional structure that enables it to engage with the target DNA.”

    “Because we now have high-resolution structures of the two major types of Cas9 proteins, we can start to see how this family of bacterial enzymes has evolved,” Doudna says. “We see that the two structures are quite different from each other outside of their catalytic domains, suggesting an interesting structural plasticity that could explain how Cas9 is able to use different kinds of guide RNAs. Also, the differences in the two structures suggest that it may be possible to engineer smaller Cas9 variants and still retain function, an important goal for some genome engineering applications.”

    two
    Eva Nogales (left) and Jennifer Doudna led a study that produced the first detailed look at the 3D structure of the Cas9 enzyme and how it partners with guide RNA. (Photo by Roy Kaltschmidt)

    Doudna and Nogales are the corresponding authors, along with Martin Jinek of the University of Zurich, of a paper in Science that describes this research. The paper is titled Structures of Cas9 endonucleases reveal RNA-mediated conformational activation. Co-authors are Fuguo Jiang, David Taylor, Samuel Sternberg, Emine Kaya, Enbo Ma, Carolin Anders, Michael Hauer, Kaihong Zhou, Steven Lin, Mattias Kaplan, Anthony Iavarone and Emmanuelle Charpentier.

    See the full article here.

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  • richardmitnick 5:01 pm on February 3, 2014 Permalink | Reply
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    From Berkeley Lab: “How a Shape-shifting DNA-repair Machine Fights Cancer” 


    Berkeley Lab

    February 03, 2014
    Dan Krotz 510-484-5956 dakrotz@lbl.gov

    Maybe you’ve seen the movies or played with toy Transformers, those shape-shifting machines that morph in response to whatever challenge they face. It turns out that DNA-repair machines in your cells use a similar approach to fight cancer and other diseases, according to research led by scientists from the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab).

    mre
    One protein complex, two very different shapes and functions: In the top image, the scientists created an Mre11-Rad50 mutation that speeds up hydrolysis, yielding an open state that favors a high-fidelity way to repair DNA. In the bottom image, the scientists slowed down hydrolysis, resulting in a closed ATP-bound state that favors low-fidelity DNA repair. (Credit: Tainer lab)

    As reported in a pair of new studies, the scientists gained new insights into how a protein complex called Mre11-Rad50 reshapes itself to take on different DNA-repair tasks.

    Their research sheds light on how this molecular restructuring leads to different outcomes in a cell. It could also guide the development of better cancer-fighting therapies and more effective gene therapies.

    As reported in a pair of new studies, the scientists gained new insights into how a protein complex called Mre11-Rad50 reshapes itself to take on different DNA-repair tasks.

    Their research sheds light on how this molecular restructuring leads to different outcomes in a cell. It could also guide the development of better cancer-fighting therapies and more effective gene therapies.

    Mre11-Rad50’s job is the same in your cells, your pet’s cells, or any organism’s. It detects and helps fix the gravest kind of DNA breaks in which both strands of a DNA double helix are cut. The protein complex binds to the broken DNA ends, sends out a signal that stops the cell from dividing, and uses its shape-shifting ability to choose which DNA repair process is launched to fix the broken DNA. If unrepaired, double strand breaks are lethal to the cell. In addition, a repair job gone wrong can lead to the proliferation of cancer cells.

    Little is known about how the protein’s Transformer-like capabilities relate to its DNA-repair functions, however.

    To learn more, the scientists modified the protein complex in ways that were designed to affect just one of the many activities it undertakes. They then used structural biology, biochemistry, and genomic tools to study the impacts of these modifications.

    “By targeting a single activity, we can make the protein complex go down a different pathway and learn how its dynamic structure changes,” says John Tainer of Berkeley Lab’s Life Sciences Division. He conducted the research with fellow Berkeley Lab scientist Gareth Williams and scientists from several other institutions.

    Adds Williams, “In some cases, we sped up or slowed down the protein complex’s movements, and by doing so we changed its biological outcomes.”

    sybll
    Much of the research was conducted at the SIBYLS beamline at the Advanced Light Source. SIBYLS stands for Structurally Integrated Biology for Life Sciences.

    Much of the research was conducted at the Advanced Light Source (ALS), a synchrotron located at Berkeley Lab that generates intense X-rays to probe the fundamental properties of substances. They used an ALS beamline called SYBILS, which combines X-ray scattering with X-ray diffraction capabilities. It yields atomic-resolution images of the crystal structures of proteins. It can also watch the transformation of the protein as it undergoes conformational changes.

    In one study published in the journal Molecular Cell, the scientists studied Mre11 from microbial cells. They developed two molecular inhibitors that block Mre11’s ability to cut DNA, a critical initial step in the repair process.

    They tested the effect of these inhibitors in human cells. They found that Mre11 first makes a nick away from the broken DNA strand it is repairing. Mre11 then works back toward the broken end. Previously, scientists thought that Mre11 always starts at the broken DNA end. They also found that when Mre11 cuts in the middle of a DNA strand, it initiates a high-precision DNA-repair pathway called homologous recombination repair.

    In another study published in EMBO Journal, the scientists created Rad50 mutations that either promote or destabilize the shape formed when the Rad50 subunit binds with ATP, a chemical that fuels the protein complex’s movements.

    Biochemical and functional assays conducted by Tanya Paull of the University of Texas at Austin revealed how these changes affect microbial, yeast, and human Mre11-Rad50 activities. Paul Russell at the Scripps Research Institute helped the scientists learn how these Rad50 mutations affect yeast cells.

    They found that some mutations slowed down ATP hydrolysis, which is how Rad50 and other enzymes use ATP as fuel. Other mutations sped it up. Both changes affected Mre11-Rad50’s workflow, and its biological outcomes, in a big way.

    “When we slowed down hydrolysis and favored the ATP-bound state, Rad50 favored a non-homologous end joining pathway, which is a low-fidelity way to repair DNA,” says Williams. “When we sped it up, the subunit favored homologous repair, which is the high-fidelity pathway.”

    This approach, in which scientists start with a specific protein mechanism and learn how it affects the entire organism, will help researchers develop a predictive understanding of how Mre11-Rad50 works.

    “It’s a ‘bottom up’ way to study proteins such as Mre11-Rad50, and it could guide the development of better cancer therapies and other applications,” says Tainer.

    See the full article, with further material, here.

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  • richardmitnick 4:27 pm on November 22, 2013 Permalink | Reply
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    From Berkeley Lab: “An Inside Look at a MOF in Action” 


    Berkeley Lab

    Berkeley Lab Researchers Probe Into Electronic Structure of MOF May Lead to Improved Capturing of Greenhouse Gases

    November 22, 2013
    Lynn Yarris (510) 486-5375 lcyarris@lbl.gov

    A unique inside look at the electronic structure of a highly touted metal-organic framework (MOF) as it is adsorbing carbon dioxide gas should help in the design of new and improved MOFs for carbon capture and storage. Researchers with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) have recorded the first in situ electronic structure observations of the adsorption of carbon dioxide inside Mg-MOF-74, an open metal site MOF that has emerged as one of the most promising strategies for capturing and storing greenhouse gases.

    Working at Berkeley Lab’s Advanced Light Source (ALS), a team led by Jeff Kortright of Berkeley Lab’s Materials Sciences Division, used the X-ray spectroscopy technique known as Near Edge X-ray Absorption Fine Structure (NEXAFS) to obtain what are believed to be the first ever measurements of chemical and electronic signatures inside of a MOF during gas adsorption.

    “We’ve demonstrated that NEXAFS spectroscopy is an effective tool for the study of MOFs and gas adsorption,” Kortright says. “Our study shows that open metal site MOFs have significant X-ray spectral signatures that are highly sensitive to the adsorption of carbon dioxide and other molecules.”

    Kortright is the corresponding author of a paper describing these results in the Journal of the American Chemical Society (JACS). The paper is titled Probing Adsorption Interactions In Metal-Organic Frameworks Using X-ray Spectroscopy. Co-authors are Walter Drisdell, Roberta Poloni, Thomas McDonald, Jeffrey Long, Berend Smit, Jeffrey Neaton and David Prendergast.

    spec
    Mg-MOF-74 is an open metal site MOF whose porous crystalline structure could enable it to serve as a storage vessel for capturing and containing the carbon dioxide emitted from coal-burning power plants. (National Academy of Sciences)

    See the full article here.

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  • richardmitnick 6:35 pm on November 18, 2013 Permalink | Reply
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    From Berkeley Lab: “A Superconductor-Surrogate Earns Its Stripes” 


    Berkeley Lab

    November 18, 2013
    Berkeley Lab Study Reveals Origins of an Exotic Phase of Matter

    Alison Hatt 510-486-7154 ajhatt@lbl.gov

    Understanding superconductivity – whereby certain materials can conduct electricity without any loss of energy – has proved to be one of the most persistent problems in modern physics. Scientists have struggled for decades to develop a cohesive theory of superconductivity, largely spurred by the game-changing prospect of creating a superconductor that works at room temperature, but it has proved to be a tremendous tangle of complex physics.

    Now scientists at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have teased out another important tangle from this giant ball of string, bringing us a significant step closer to understanding how high- temperature superconductors work their magic. Working with a model compound, the team illuminated the origins of the so-called “stripe phase” in which electrons become concentrated in stripes throughout a material, and which appears to be linked to superconductivity.

    image
    Ultrafast changes in the optical properties of strontium-doped lanthanum nickelate throughout the infrared spectrum expose a rapid dynamics of electronic localization in the nickel-oxide plane, shown at left. This process, illustrated on the right, comprises the first step in the formation of ordered charge patterns or “stripes.”

    “We’re trying to understand nanoscale order and how that determines material properties such as superconductivity,” said Robert Kaindl, a physicist in Berkeley Lab’s Materials Sciences Division. “Using ultrafast optical techniques, we are able to observe how charge stripes start to form on a time scale of hundreds of femtoseconds.” A femtosecond is just one millionth of one billionth of a second.

    Electrons in a solid material interact extremely quickly and on very short length scales, so to observe their behavior researchers have built extraordinarily powerful “microscopes” that zoom into fast events using short flashes of laser light. Kaindl and his team brought to bear the power of their ultrafast-optics expertise to understand the stripe phase in strontium-doped lanthanum nickelate (LSNO), a close cousin of high-temperature superconducting materials.

    “We chose to work with LSNO because it has essential similarities to the cuprates (an important class of high-temperature superconductors), but its lack of superconductivity lets us focus on understanding just the stripe phase,” said Giacomo Coslovich, a postdoctoral researcher at Berkeley Lab working with Kaindl.

    “With science, you have to simplify your problems,” Coslovich continued. “If you try to solve them all at once with their complicated interplay, you will never understand what’s going on.”

    two
    Giacomo Coslovich (left) and Robert Kaindl (right) next to the laser setup that generates extremely short pulses of light at “mid-infrared” wavelengths, far beyond the spectrum perceptible by the human eye.

    Beyond the ultrafast measurements, the team also studied X-ray scattering and the infrared reflectance of the material at the neighboring Advanced Light Source, to develop a thorough, cohesive understanding of the stripe phase and why it forms.

    Said Kaindl, “We took advantage of our fortunate location in the national lab environment, where we have both these ultrafast techniques and the Advanced Light Source. This collaborative effort made this work possible.”

    See the full article here.

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  • richardmitnick 2:06 pm on July 10, 2013 Permalink | Reply
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    From Berkeley Lab: “Of Aging Bones and Sunshine” 


    Berkeley Lab

    Study at Berkeley Lab’s Advanced Light Source Links Vitamin D Deficiency to Accelerated Aging of Bones

    July 10, 2013
    Lynn Yarris (510) 486-5375 lcyarris@lbl.gov

    “Everyone knows that as we grow older our bones become more fragile. Now a team of U.S. and German scientists led by researchers with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley has shown that this bone-aging process can be significantly accelerated through deficiency of vitamin D – the sunshine vitamin.

    Vitamin D deficiency is a widespread medical condition that has been linked to the health and fracture risk of human bone on the basis of low calcium intake and reduced bone density. However, working at Berkeley Lab’s Advanced Light (ALS), a DOE national user facility, the international team demonstrated that vitamin D deficiency also reduces bone quality.

    ‘The assumption has been that the main problem with vitamin D deficiency is reduced mineralization for the creation of new bone mass, but we’ve shown that low levels of vitamin D also induces premature aging of existing bone,’ says Robert Ritchie, who led the U.S. portion of this collaboration. Ritchie holds joint appointments with Berkeley Lab’s Materials Sciences Division and the University of California (UC) Berkeley’s Materials Science and Engineering Department.

    bones
    These 3D reconstructions of crack paths show in the normal bone (left) pronounced crack deflection by splitting along the interfaces of the osteons accompanied by the formation of crack bridges. In vitamin D–deficient sample, the crack takes a tortuous breaking path across the osteons with no crack bridging. (Courtesy of Ritchie and Bale)

    ‘Unraveling the complexity of human bone structure may provide some insight into more effective ways to prevent or treat fractures in patients with vitamin D deficiency,’ says Björn Busse, of the Department of Osteology and Biomechanics at the University Medical Center in Hamburg, Germany, who led the German portion of the team.”

    See the full article here.

    Ritchie and Busse have reported their findings in the journal Science Translational Medicine.

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  • richardmitnick 10:58 am on March 13, 2013 Permalink | Reply
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    From Berkeley Lab: “Surprising Control over Photoelectrons from a Topological Insulator” 


    Berkeley Lab

    Berkeley Lab scientists discover how a photon beam can flip the spin polarization of electrons emitted from an exciting new material

    Plain-looking but inherently strange crystalline materials called 3D topological insulators (TIs) are all the rage in materials science. Even at room temperature, a single chunk of TI is a good insulator in the bulk, yet behaves like a metal on its surface.

    block
    The interior bulk of a topological insulator is indeed an insulator, but electrons (spheres) move swiftly on the surface as if through a metal. They are spin-polarized, however, with their momenta (directional ribbons) and spins (arrows) locked together. Berkeley Lab researchers have discovered that the spin polarization of photoelectrons (arrowed sphere at upper right) emitted when the material is struck with high-energy photons (blue-green waves from left) is completely determined by the polarization of this incident light. (Image Chris Jozwiak, Zina Deretsky, and Berkeley Lab Creative Services Office)

    Researchers find TIs exciting partly because the electrons that flow swiftly across their surfaces are ‘spin polarized’: the electron’s spin is locked to its momentum, perpendicular to the direction of travel. These interesting electronic states promise many uses – some exotic, like observing never-before-seen fundamental particles, but many practical, including building more versatile and efficient high-tech gadgets, or, further into the future, platforms for quantum computing.

    A team of researchers from the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California at Berkeley has just widened the vista of possibilities with an unexpected discovery about TIs: when hit with a laser beam, the spin polarization of the electrons they emit (in a process called photoemission) can be completely controlled in three dimensions, simply by tuning the polarization of the incident light.

    ‘The first time I saw this it was a shock; it was such a large effect and was counter to what most researchers had assumed about photoemission from topological insulators, or any other material,’ says Chris Jozwiak of Berkeley Lab’s Advanced Light Source (ALS), who worked on the experiment. ‘Being able to control the interaction of polarized light and photoelectron spin opens a playground of possibilities.’”

    See the full article here.

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  • richardmitnick 6:16 pm on March 3, 2013 Permalink | Reply
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    From Berkeley Lab: “Searching for the Solar System’s Chemical Recipe” 


    Berkeley Lab

    Berkeley Lab’s Chemical Dynamics Beamline points to why isotope ratios in interplanetary dust and meteorites differ from Earth’s

    February 20, 2013
    Paul Preuss

    “By studying the origins of different isotope ratios among the elements that make up today’s smorgasbord of planets, moons, comets, asteroids, and interplanetary ice and dust, Mark Thiemens and his colleagues hope to learn how our solar system evolved. Thiemens, Dean of the Division of Physical Sciences at the University of California, San Diego, has worked on this problem for over three decades.

    isotopes
    The protosun evolved in a hot nebula of infalling gas and dust that formed an accretion disk (green) of surrounding matter. Visible and ultraviolet light poured from the sun, irradiating abundant clouds of carbon monoxide, hydrogen sulfide, and other chemicals. Temperatures near the sun were hot enough to melt silicates and other minerals, forming the chondrules found in early meteoroids (dashed black circles). Beyond the “snowline” (dashed white curves), water, methane, and other compounds condensed to ice. Numerous chemical reactions contributed to the isotopic ratios seen in relics of the early solar system today.

    In recent years his team has found the Chemical Dynamics Beamline of the Advanced Light Source (ALS) at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) to be an invaluable tool for examining how photochemistry determines the basic ingredients in the solar system recipe.

    ‘Mark and his colleagues Subrata Chakraborty and Teresa Jackson wanted to know if photochemistry could explain some of the differences in isotope ratios between Earth and what’s found in meteorites and interplanetary dust particles,’ says Musahid (Musa) Ahmed of Berkeley Lab’s Chemical Sciences Division, a scientist at the Chemical Dynamics Beamline who works with the UC San Diego team. ‘They needed a source of ultraviolet light powerful enough to dissociate gas molecules like carbon monoxide, hydrogen sulfide, and nitrogen. That’s us: our beamline basically provides information about gas-phase photodynamics.’”

    At this point, I direct you to the full article. There is a lot going on here.

    A U.S. Department of Energy National Laboratory Operated by the University of California

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  • richardmitnick 2:27 pm on February 20, 2013 Permalink | Reply
    Tags: , Berkeley ALS, , ,   

    From Berkeley Lab: “Searching for the Solar System’s Chemical Recipe” 


    Berkeley Lab

    Berkeley Lab’s Chemical Dynamics Beamline points to why isotope ratios in interplanetary dust and meteorites differ from Earth’s

    February 20, 2013
    Paul Preuss

    disc
    The protosun evolved in a hot nebula of infalling gas and dust that formed an accretion disk (green) of surrounding matter. Visible and ultraviolet light poured from the sun, irradiating abundant clouds of carbon monoxide, hydrogen sulfide, and other chemicals. Temperatures near the sun were hot enough to melt silicates and other minerals, forming the chondrules found in early meteoroids (dashed black circles). Beyond the “snowline” (dashed white curves), water, methane, and other compounds condensed to ice. Numerous chemical reactions contributed to the isotopic ratios seen in relics of the early solar system today. No image credit.

    “By studying the origins of different isotope ratios among the elements that make up today’s smorgasbord of planets, moons, comets, asteroids, and interplanetary ice and dust, Mark Thiemens and his colleagues hope to learn how our solar system evolved. Thiemens, Dean of the Division of Physical Sciences at the University of California, San Diego, has worked on this problem for over three decades.

    In recent years his team has found the Chemical Dynamics Beamline of the Advanced Light Source (ALS) at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) to be an invaluable tool for examining how photochemistry determines the basic ingredients in the solar system recipe.

    ‘Mark and his colleagues Subrata Chakraborty and Teresa Jackson wanted to know if photochemistry could explain some of the differences in isotope ratios between Earth and what’s found in meteorites and interplanetary dust particles,’ says Musahid (Musa) Ahmed of Berkeley Lab’s Chemical Sciences Division, a scientist at the Chemical Dynamics Beamline who works with the UC San Diego team. ‘They needed a source of ultraviolet light powerful enough to dissociate gas molecules like carbon monoxide, hydrogen sulfide, and nitrogen. That’s us: our beamline basically provides information about gas-phase photodynamics.’”

    See the full article here.

    A U.S. Department of Energy National Laboratory Operated by the University of California

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