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  • richardmitnick 10:22 am on March 25, 2019 Permalink | Reply
    Tags: , , For Phase 3 installation of the full decay VerteX Detector (VXD) was completed. With this change Belle II is now fully equipped and ready to take physics data., , KEK Inter-University Research Institute Corporation, Nanotechnology, ,   

    From KEK Inter-University Research Institute Corporation: “SuperKEKB Phase 3 (Belle II Physics Run) Starts” 

    From KEK Inter-University Research Institute Corporation

    2019/03/11

    On March 11th, 2019, Phase 3 operation of the SuperKEKB project began successfully, marking a major milestone in the development of Japan’s leading particle collider. This phase will be the physics run of the project, in which the Belle II experiment will start taking data with a fully instrumented detector.

    The KEKB accelerator, operated from 1999 to 2010, currently holds the world record luminosity for an electron-positron collider. SuperKEKB, its successor, plans to reach a luminosity 40 times greater over its lifetime.

    Belle II and SuperKEKB are poised to become the world’s first Super B factory facility. Belle II aims to accumulate 50 times more data than its predecessor, Belle, and to seek out new physics hidden in subatomic particles that could shed light on mysteries of the early universe.

    Belle II KEK High Energy Accelerator Research Organization Tsukuba, Japan

    The Belle experiment, which completed data taking in 2010, along with its competitor in the United States BaBar, demonstrated Charge-Parity Violation (CPV) in weak interactions of B mesons.

    SLAC BaBar


    SLAC BaBar

    This discovery was explicitly recognized by the Nobel Foundation and resulted in the 2008 Nobel Prize for Physics being awarded to Professors Makoto Kobayashi and Toshihide Maskawa for their work developing the theory of CPV in weak interactions.

    A major upgrade, the Belle II/SuperKEKB facility, began construction at the end of 2010. SuperKEKB will achieve its goal of 40 times KEKB’s luminosity by shrinking the beams to “nano-beam” size, at the collision point, 20 times smaller than the beam sizes achieved at KEKB while simultaneously doubling the beam currents. These changes will result in much larger quantities of data as well as greater beam backgrounds. Belle II was designed to handle these conditions.

    In February 2016, Phase 1 commissioning of the SuperKEKB accelerator was successfully completed. Low-emittance Ampère-level beams were circulated in both rings, but no collisions were possible. This was followed by the installation of the superconducting final focus magnets and the Belle II outer detector. Phase 2, the pilot run of Belle II, began in March of 2018, with the first collisions recorded in the early hours of April 26th. Initial results from Phase 2 were shown at international conferences in 2018.

    For Phase 3, installation of the full decay VerteX Detector (VXD) was completed. With this change, Belle II is now fully equipped and ready to take physics data.

    See the full article here .

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    KEK-Accelerator Laboratory

    KEK, the High Energy Accelerator Research Organization, is one of the world’s leading accelerator science research laboratories, using high-energy particle beams and synchrotron light sources to probe the fundamental properties of matter. With state-of-the-art infrastructure, KEK is advancing our understanding of the universe that surrounds us, its mechanisms and their control. Our mission is:

    • To make discoveries that address the most compelling questions in a wide range of fields, including particle physics, nuclear physics, materials science, and life science. We at KEK strive to make the most effective use of the funds entrusted by Japanese citizens for the benefit of all, by adding to knowledge and improving the technology that protects the environment and serves the economy, academia, and public health; and

    • To act as an Inter-University Research Institute Corporation, a center of excellence that promotes academic research by fulfilling the needs of researchers in universities across the country and by cooperating extensively with researchers abroad; and

    • To promote national and international collaborative research activities by providing advanced research facilities and opportunities. KEK is committed to be in the forefront of accelerator science in Asia-Oceania, and to cooperate closely with other institutions, especially with Asian laboratories.

    Established in 1997 in a reorganization of the Institute of Nuclear Study, University of Tokyo (established in 1955), the National Laboratory for High Energy Physics (established in 1971), and the Meson Science Laboratory of the University of Tokyo (established in 1988), KEK serves as a center of excellence for domestic and foreign researchers, providing a wide variety of research opportunities. In addition to the activities at the Tsukuba Campus, KEK is now jointly operating a high-intensity proton accelerator facility (J-PARC) in Tokai village, together with the Japan Atomic Energy Agency (JAEA). Over 600 scientists, engineers, students and staff perform research activities on the Tsukuba and Tokai campuses. KEK attracts nearly 100,000 national and international researchers every year (total man-days), and provides excellent research facilities and opportunities to many students and post-doctoral fellows each year.

     
  • richardmitnick 11:42 am on March 22, 2019 Permalink | Reply
    Tags: Nanotechnology, , , Ultraviolet light-emitting diodes   

    From NIST: “NIST Researchers Boost Intensity of Nanowire LEDs” 


    From NIST

    March 21, 2019

    Laura Ost
    laura.ost@nist.gov
    (303) 497-4880

    1
    Model of nanowire-based light-emitting diode showing that adding a bit of aluminum to the shell layer (black) directs all recombination of electrons and holes (spaces for electrons) into the nanowire core (multicolored region), producing intense light. Credit: NIST

    Nanowire gurus at the National Institute of Standards and Technology (NIST) have made ultraviolet light-emitting diodes (LEDs) that, thanks to a special type of shell, produce five times higher light intensity than do comparable LEDs based on a simpler shell design.

    Ultraviolet LEDs are used in a growing number of applications such as polymer curing, water purification and medical disinfection. Micro-LEDs are also of interest for visual displays. NIST staff are experimenting with nanowire-based LEDs for scanning-probe tips intended for electronics and biology applications.

    The new, brighter LEDs are an outcome of NIST’s expertise in making high-quality gallium nitride (GaN) nanowires. Lately, researchers have been experimenting with nanowire cores made of silicon-doped GaN, which has extra electrons, surrounded by shells made of magnesium-doped GaN, which has a surplus of “holes” for missing electrons. When an electron and a hole combine, energy is released as light, a process known as electroluminescence.

    The NIST group previously demonstrated GaN LEDs that produced light attributed to electrons injected into the shell layer to recombine with holes. The new LEDs have a tiny bit of aluminum added to the shell layer, which reduces losses from electron overflow and light reabsorption.

    As described in the journal Nanotechnology, the brighter LEDs are fabricated from nanowires with a so-called “p-i-n” structure, a tri-layer design that injects electrons and holes into the nanowire. The addition of aluminum to the shell helps confine electrons to the nanowire core, boosting the electroluminescence fivefold.

    “The role of the aluminum is to introduce an asymmetry in the electrical current that prevents electrons from flowing into the shell layer, which would reduce efficiency, and instead confines electrons and holes to the nanowire core,” first author Matt Brubaker said.

    The nanowire test structures were about 440 nanometers (nm) long with a shell thickness of about 40 nm. The final LEDs, including the shells, were almost 10 times larger. Researchers found that the amount of aluminum incorporated into fabricated structures depends on nanowire diameter.

    Group leader Kris Bertness said at least two companies are developing micro-LEDs based on nanowires, and NIST has a Cooperative Research and Development Agreement with one of them to develop dopant and structural characterization methods. The researchers have had preliminary discussions with scanning-probe companies about using NIST LEDs in their probe tips, and NIST plans to demonstrate prototype LED tools soon.

    The NIST team holds U.S. Patent 8,484,756 on an instrument that combines microwave scanning probe microscopy with an LED for nondestructive, contactless testing of material quality for important semiconductor nanostructures such as transistor channels and individual grains in solar cells. The probe could also be used for biological research on protein unfolding and cell structure.

    See the full article here.

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    NIST Campus, Gaitherberg, MD, USA

    NIST Mission, Vision, Core Competencies, and Core Values

    NIST’s mission

    To promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life.
    NIST’s vision

    NIST will be the world’s leader in creating critical measurement solutions and promoting equitable standards. Our efforts stimulate innovation, foster industrial competitiveness, and improve the quality of life.
    NIST’s core competencies

    Measurement science
    Rigorous traceability
    Development and use of standards

    NIST’s core values

    NIST is an organization with strong values, reflected both in our history and our current work. NIST leadership and staff will uphold these values to ensure a high performing environment that is safe and respectful of all.

    Perseverance: We take the long view, planning the future with scientific knowledge and imagination to ensure continued impact and relevance for our stakeholders.
    Integrity: We are ethical, honest, independent, and provide an objective perspective.
    Inclusivity: We work collaboratively to harness the diversity of people and ideas, both inside and outside of NIST, to attain the best solutions to multidisciplinary challenges.
    Excellence: We apply rigor and critical thinking to achieve world-class results and continuous improvement in everything we do.

     
  • richardmitnick 8:39 am on March 21, 2019 Permalink | Reply
    Tags: "Superconducting nanowires could be used to detect dark matter", A promising new sensor based on tiny superconducting wires, , , Nanotechnology, , The team’s prototype already shows the potential of this approach, Yonit Hochberg at Hebrew University of Jerusalem in Israel and a few colleagues   

    From M.I.T. Technology Review: “Superconducting nanowires could be used to detect dark matter” 

    MIT Technology Review
    From M.I.T. Technology Review

    1

    March 20, 2019
    No writer credit or image credits

    One of the great scientific searches of our time is the hunt for dark matter. Physicists believe this stuff fills the universe and think they can see evidence of it in the way galaxies rotate. Indeed, galaxies spin so quickly that they ought to fly apart unless some hidden mass is generating enough gravitational force to hold them together.

    That evidence has set physicists scrabbling to find dark matter on Earth. They’ve constructed dozens of observatories, most of them in underground caverns deep beneath the surface, where background noise is low. At stake is scientific fame and fortune, with the group that finds dark matter likely to be richly rewarded.

    But so far physicists have found precisely nothing. If it is out there, dark matter is very well hidden. Or physicists have been looking in the wrong place. One possibility is that dark matter particles are too small for current experiments to see. So physicists desperately want better, more sensitive ways to detect these things.

    2

    Enter Yonit Hochberg at Hebrew University of Jerusalem in Israel and a few colleagues, who have developed a promising new sensor based on tiny superconducting wires. The team’s prototype already shows the potential of this approach.

    The principle behind the new device is straightforward. Cool certain metals below a critical temperature and they conduct with no resistance. But as soon as their temperature rises above this threshold, the superconducting behavior disappears.

    Physicists know that dark matter particles cannot interact strongly with visible matter; otherwise they would have already seen them. But dark matter particles can collide head-on with ordinary particles.

    These collisions are rare because ordinary matter is mostly empty space, so dark matter particles can pass straight through. But when they do collide with an atomic nucleus or electron in a lattice, for example, the collision causes the lattice to vibrate, thereby raising its temperature.

    It is this rise in temperature that superconducting nanowires are good at revealing. The heating causes a small portion of the wire to stop superconducting, and this in turn creates a voltage pulse that is easy to measure. What’s more, such a device produces few, if any, false positives.

    Hochberg and Co have put their idea through its paces by building a prototype. This device consists of set of tungsten silicide nanowires just 140 nanometers wide (a human hair is about 100,000 nanometers wide) and 400 micrometers long. The entire apparatus sits just a few millidegrees above absolute zero, so that the tungsten silicide wires become superconductors.

    The team then looked for the voltage pulses that might reveal a dark matter collision. With appropriate shielding in place, they found no pulses during the 10,000-second duration of their measurements.

    That places important constraints on the type of dark matter that could be present and its density. It also places constraints on other types of particles that physicists speculate might exist.

    One of these is the “dark photon”—essentially the dark matter equivalent of the ordinary photon. If they exist, then the new sensor did not detect a single one. “The results from this device already place meaningful bounds on dark matter-electron interactions, including the strongest terrestrial bounds on sub-eV dark photon absorption to date,” say Hochberg and Co.

    That’s impressive work, given that the mass of the nanowires is just a few nanograms. The next stage is to fabricate them on a larger scale. Hochberg and co say that the technology is relatively mature, so this should be possible on a short time scale. Indeed, they estimate that an academic lab could churn out a thousand 200-nanometer detectors with a total mass of 1.3 grams in just a year. “An industrial effort could realize many times that number,” they point out.

    So a kilogram-scale detector could be feasible in the not too distant future. Such a machine would rival those already in operation in the search for dark matter, but it would look at different energies in a different way.

    So it may be that one day, superconducting nanowires will discover dark matter—if it exists at all.

    Science paper:
    Detecting Dark Matter with Superconducting Nanowires
    https://arxiv.org/pdf/1903.05101.pdf

    See the full article here .


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    Stem Education Coalition

    The mission of MIT Technology Review is to equip its audiences with the intelligence to understand a world shaped by technology.

     
  • richardmitnick 8:16 am on March 19, 2019 Permalink | Reply
    Tags: Ames Laboratory, , , Iowa State University, Janus nanocrystal platform, MSE-Material Science and Engineering, Nanoparticle self-assembly, Nanotechnology,   

    From Iowa State University: “Engineered nanoparticle discovery led by MSE’s Jiang makes cover of Nano Letters” 

    Iowa State University

    March 13, 2019
    Cyclone Engineering

    1

    Shan Jiang, assistant professor of material science and engineering [MSE], led a research group that created a novel Janus nanocrystal platform to control nanoparticle self-assembly.

    Janus particles are fundamental new materials, and Jiang’s discovery opens opportunities in different areas including energy, drug delivery, disease diagnosis and therapy. The results appear on the cover of the March issue of Nano Letters.

    Key to the team’s discoveries were a multidisciplinary approach and the powerful high-resolution scanning transmission electron microscopy available at U.S. Department of Energy’s Ames Laboratory’s Sensitive Instrument Facility.

    Ames Lab’s Matt Kramer with the Tecnai transmission electron microscope at the new Sensitive Instrument Facility

    The collaborative research effort is led by Jiang with Eric Cochran, professor of chemical and biological engineering, and Lin Zhou, scientist at Ames Laboratory. Fei Liu, a postdoctoral researcher in materials science and engineering, is the first author. Shailja Goyal and Michael Forrester, graduate students in chemical and biological engineering, contributed to the synthesis and Tao Ma, a postdoctoral researcher at Ames Laboratory contributed to the electron microscopy characterization. Undergraduates in materials science and engineering Yasmeen Mansoorieh and John Henjum also contributed to the work.

    Jiang’s research team’s technique is inexpensive, scalable to commercial production. The group demonstrated their synthesis approach in the form of Au-Fe3O4 nanocrystals, particularly important materials because the particles are biocompatible and have enhanced magnetic and surface plasmon resonance properties.

    “We had the right people and the right facilities to demonstrate for the first time that we can make these particles that show unique structures. The work was all completed here on the Iowa State University campus, and I’m very proud of that,” said Jiang.

    See the full article here .

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    Stem Education Coalition

    Iowa State University is a public, land-grant university, where students get a great academic start in learning communities and stay active in 800-plus student organizations, undergrad research, internships and study abroad. They learn from world-class scholars who are tackling some of the world’s biggest challenges — feeding the hungry, finding alternative fuels and advancing manufacturing.

    Iowa Agricultural College and Model Farm (now Iowa State University) was officially established on March 22, 1858, by the legislature of the State of Iowa. Story County was selected as a site on June 21, 1859, and the original farm of 648 acres was purchased for a cost of $5,379. The Farm House, the first building on the Iowa State campus, was completed in 1861, and in 1862, the Iowa legislature voted to accept the provision of the Morrill Act, which was awarded to the agricultural college in 1864.

    Iowa State University Knapp-Wilson Farm House. Photo between 1911-1926

    Iowa Agricultural College (Iowa State College of Agricultural and Mechanic Arts as of 1898), as a land grant institution, focused on the ideals that higher education should be accessible to all and that the university should teach liberal and practical subjects. These ideals are integral to the land-grant university.

    The first official class entered at Ames in 1869, and the first class (24 men and 2 women) graduated in 1872. Iowa State was and is a leader in agriculture, engineering, extension, home economics, and created the nation’s first state veterinary medicine school in 1879.

    In 1959, the college was officially renamed Iowa State University of Science and Technology. The focus on technology has led directly to many research patents and inventions including the first binary computer (the ABC), Maytag blue cheese, the round hay baler, and many more.

    Beginning with a small number of students and Old Main, Iowa State University now has approximately 27,000 students and over 100 buildings with world class programs in agriculture, technology, science, and art.

    Iowa State University is a very special place, full of history. But what truly makes it unique is a rare combination of campus beauty, the opportunity to be a part of the land-grant experiment, and to create a progressive and inventive spirit that we call the Cyclone experience. Appreciate what we have here, for it is indeed, one of a kind.

     
  • richardmitnick 2:47 pm on March 15, 2019 Permalink | Reply
    Tags: Nanotechnology, , , Quantum information can be stored and exchanged using electron spin states., , Size matters in quantum information exchange even on the nanometer scale, The collaboration between researchers with diverse expertise was key to success., Two correlated electron pairs were coherently superposed and entangled over five quantum dots constituting a new world record within the community.   

    From Niels Bohr Institute: “Long-distance quantum information exchange – success at the nanoscale” 

    University of Copenhagen

    Niels Bohr Institute bloc

    From Niels Bohr Institute

    At the Niels Bohr Institute, University of Copenhagen, researchers have realized the swap of electron spins between distant quantum dots. The discovery brings us a step closer to future applications of quantum information, as the tiny dots have to leave enough room on the microchip for delicate control electrodes. The distance between the dots has now become big enough for integration with traditional microelectronics and perhaps, a future quantum computer. The result is achieved via a multinational collaboration with Purdue University and the University of Sydney, Australia, now published in Nature Communications.

    Size matters in quantum information exchange even on the nanometer scale.

    Quantum information can be stored and exchanged using electron spin states. The electrons’ charge can be manipulated by gate-voltage pulses, which also controls their spin. It was believed that this method can only be practical if quantum dots touch each other; if squeezed too close together the spins will react too violently, if placed too far apart the spins will interact far too slowly. This creates a dilemma, because if a quantum computer is ever going to see the light of day, we need both, fast spin exchange and enough room around quantum dots to accommodate the pulsed gate electrodes.

    Normally, the left and right dots in the linear array of quantum dots (Illustration 1) are too far apart to exchange quantum information with each other. Frederico Martins, postdoc at UNSW, Sydney, Australia, explains: “We encode quantum information in the electrons’ spin states, which have the desirable property that they don’t interact much with the noisy environment, making them useful as robust and long-lived quantum memories. But when you want to actively process quantum information, the lack of interaction is counterproductive – because now you want the spins to interact!” What to do? You can’t have both long lived information and information exchange – or so it seems. “We discovered that by placing a large, elongated quantum dot between the left dots and right dots, it can mediate a coherent swap of spin states, within a billionth of a second, without ever moving electrons out of their dots. In other words, we now have both fast interaction and the necessary space for the pulsed gate electrodes ”, says Ferdinand Kuemmeth, associate professor at the Niels Bohr Institute.

    1
    Researchers at the Niels Bohr Institute cooled a chip containing a large array of spin qubits below -273 Celsius. To manipulate individual electrons within the quantum-dot array, they applied fast voltage pulses to metallic gate electrodes located on the surface of the gallium-arsenide crystal (see scanning electron micrograph). Because each electron also carries a quantum spin, this allows quantum information processing based on the array’s spin states (the arrows on the graphic illustration). During the mediated spin exchange, which only took a billionth of a second, two correlated electron pairs were coherently superposed and entangled over five quantum dots, constituting a new world record within the community.

    Collaborations are an absolute necessity, both internally and externally.

    The collaboration between researchers with diverse expertise was key to success. Internal collaborations constantly advance the reliability of nanofabrication processes and the sophistication of low-temperature techniques. In fact, at the Center for Quantum Devices, major contenders for the implementation of solid-state quantum computers are currently intensely studied, namely semiconducting spin qubits, superconducting gatemon qubits, and topological Majorana qubits.

    All of them are voltage-controlled qubits, allowing researchers to share tricks and solve technical challenges together. But Kuemmeth is quick to add that “all of this would be futile if we didn’t have access to extremely clean semiconducting crystals in the first place”. Michael Manfra, Professor of Materials Engineering, agrees: “Purdue has put a lot of work into understanding the mechanisms that lead to quiet and stable quantum dots. It is fantastic to see this work yield benefits for Copenhagen’s novel qubits”.

    The theoretical framework of the discovery is provided by the University of Sydney, Australia. Stephen Bartlett, a professor of quantum physics at the University of Sydney, said: “What I find exciting about this result as a theorist, is that it frees us from the constraining geometry of a qubit only relying on its nearest neighbours”. His team performed detailed calculations, providing the quantum mechanical explanation for the counterintuitive discovery.

    Overall, the demonstration of fast spin exchange constitutes not only a remarkable scientific and technical achievement, but may have profound implications for the architecture of solid-state quantum computers. The reason is the distance: “If spins between non-neighboring qubits can be controllably exchanged, this will allow the realization of networks in which the increased qubit-qubit connectivity translates into a significantly increased computational quantum volume”, predicts Kuemmeth.

    See the full article here .


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    Stem Education Coalition

    Niels Bohr Institute Campus

    Niels Bohr Institute (Danish: Niels Bohr Institutet) is a research institute of the University of Copenhagen. The research of the institute spans astronomy, geophysics, nanotechnology, particle physics, quantum mechanics and biophysics.

    The Institute was founded in 1921, as the Institute for Theoretical Physics of the University of Copenhagen, by the Danish theoretical physicist Niels Bohr, who had been on the staff of the University of Copenhagen since 1914, and who had been lobbying for its creation since his appointment as professor in 1916. On the 80th anniversary of Niels Bohr’s birth – October 7, 1965 – the Institute officially became The Niels Bohr Institute.[1] Much of its original funding came from the charitable foundation of the Carlsberg brewery, and later from the Rockefeller Foundation.[2]

    During the 1920s, and 1930s, the Institute was the center of the developing disciplines of atomic physics and quantum physics. Physicists from across Europe (and sometimes further abroad) often visited the Institute to confer with Bohr on new theories and discoveries. The Copenhagen interpretation of quantum mechanics is named after work done at the Institute during this time.

    On January 1, 1993 the institute was fused with the Astronomic Observatory, the Ørsted Laboratory and the Geophysical Institute. The new resulting institute retained the name Niels Bohr Institute.

    The University of Copenhagen (UCPH) (Danish: Københavns Universitet) is the oldest university and research institution in Denmark. Founded in 1479 as a studium generale, it is the second oldest institution for higher education in Scandinavia after Uppsala University (1477). The university has 23,473 undergraduate students, 17,398 postgraduate students, 2,968 doctoral students and over 9,000 employees. The university has four campuses located in and around Copenhagen, with the headquarters located in central Copenhagen. Most courses are taught in Danish; however, many courses are also offered in English and a few in German. The university has several thousands of foreign students, about half of whom come from Nordic countries.

    The university is a member of the International Alliance of Research Universities (IARU), along with University of Cambridge, Yale University, The Australian National University, and UC Berkeley, amongst others. The 2016 Academic Ranking of World Universities ranks the University of Copenhagen as the best university in Scandinavia and 30th in the world, the 2016-2017 Times Higher Education World University Rankings as 120th in the world, and the 2016-2017 QS World University Rankings as 68th in the world. The university has had 9 alumni become Nobel laureates and has produced one Turing Award recipient

     
  • richardmitnick 12:27 pm on March 8, 2019 Permalink | Reply
    Tags: "Scientists Take a Deep Dive Into the Imperfect World of 2D Materials", (Raman/photoluminescence spectroscopy) to study how light interacts with the electrons at microscope scales was used, A form of AFM (atomic force microscopy) was used to view structural details approaching the atomic scale, Adam Schwartzberg: “Now that we know what defects we have and what effect they have on the properties of the material we can use this information to reduce or eliminate defects, , “It’s a very big advance to get this electronic structure on small length scales” said Eli Rotenberg, Because research of WS2 and related 2D materials is still in its infancy there are many unknowns about the roles specific types of defects play in these materials, For this study the defects were due to the sample-growth process, , , Most of the experiments focused on a single flake of tungsten disulfide, NanoARPES which researchers enlisted to probe the 2D samples with X-rays was used in this work, Nanotechnology, Researchers from the Berkeley Lab Chemical Sciences Division Aarhus University in Denmark and Montana State University also participated in this study., Researchers hope to control the amount and kinds of atoms that are affected and the locations where these defects are concentrated in the flakes., The defects were largely concentrated around the edges of the flakes a signature of the growth process, The sample used in the study contained microscopic roughly triangular flakes each measuring about 1 to 5 microns (millionths of a meter) across, The team also enlisted a technique known as XPS (X-ray photoelectron spectroscopy) to study the chemical makeup of a sample at very small scales, The various techniques were applied at the Molecular Foundry where the material was synthesized and at the ALS, The X-rays knocked out electrons in the sample allowing researchers to measure their direction and energy, These 2D materials could also be incorporated in new forms of memory storage and data transfer such as spintronics and valleytronics, They were grown atop titanium dioxide crystals using a conventional layering process known as chemical vapor deposition, This revealed nanoscale defects and how the electrons interact with each other.,   

    From Lawrence Berkeley National Lab: “Scientists Take a Deep Dive Into the Imperfect World of 2D Materials” 

    Berkeley Logo

    From Lawrence Berkeley National Lab

    March 8, 2019

    Glenn Roberts Jr.
    geroberts@lbl.gov
    (510) 486-5582

    Berkeley Lab-led team combines several nanoscale techniques to gain new insights on the effects of defects in a well-studied monolayer material.

    1
    This animation displays a scan of arrow-shaped flakes of a 2D material. Samples were scanned across their electron energy, momentum, and horizontal and vertical coordinates using an X-ray-based technique known as nanoARPES at Berkeley Lab’s Advanced Light Source. Red represents the highest intensity measured, followed by orange, yellow, green, and blue, and purple (least intense). (Credit: Roland Koch/Berkeley Lab)

    Nothing is perfect, or so the saying goes, and that’s not always a bad thing. In a study at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), scientists learned how nanoscale defects can enhance the properties of an ultrathin, so-called 2D material.

    They combined a toolbox of techniques to home in on natural, nanoscale defects formed in the manufacture of tiny flakes of a monolayer material known as tungsten disulfide (WS2) and measured their electronic effects in detail not possible before.

    “Usually we say that defects are bad for a material,” said Christoph Kastl, a postdoctoral researcher at Berkeley Lab’s Molecular Foundry and the lead author of the study, published in the journal ACS Nano. “Here they provide functionality.”

    Tungsten disulfide is a well-studied 2D material that, like other 2D materials of its kind, exhibits special properties because of its atomic thinness. It is particularly well-known for its efficiency in absorbing and emitting light, and it is a semiconductor.

    Members of this family of 2D materials could serve as high-efficiency computer transistors and as other electronics components, and they also are prime candidates for use in ultrathin, high-efficiency solar cells and LED lighting, as well as in quantum computers.

    These 2D materials could also be incorporated in new forms of memory storage and data transfer, such as spintronics and valleytronics, that would revolutionize electronics by making use of materials in new ways to make smaller and more efficient devices.

    The latest result marks the first comprehensive study at the Lab’s Advanced Light Source (ALS) involving a technique called nanoARPES, which researchers enlisted to probe the 2D samples with X-rays.

    LBL ALS

    The X-rays knocked out electrons in the sample, allowing researchers to measure their direction and energy. This revealed nanoscale defects and how the electrons interact with each other.

    The nanoARPES capability is housed in an X-ray beamline, launched in 2016, known as MAESTRO (Microscopic and Electronic Structure Observatory). It is one of dozens of specialized beamlines at the ALS, which produces light in different forms – from infrared to X-rays – for a variety of simultaneous experiments.

    “It’s a very big advance to get this electronic structure on small length scales,” said Eli Rotenberg, a senior staff scientist at the ALS who was a driving force in developing MAESTRO and served as one of the study’s leaders. “That matters for real devices.”

    The team also enlisted a technique known as XPS (X-ray photoelectron spectroscopy) to study the chemical makeup of a sample at very small scales; a form of AFM (atomic force microscopy) to view structural details approaching the atomic scale; and a combined form of optical spectroscopy (Raman/photoluminescence spectroscopy) to study how light interacts with the electrons at microscope scales.

    The various techniques were applied at the Molecular Foundry, where the material was synthesized, and at the ALS.

    LBNL Molecular Foundry

    The sample used in the study contained microscopic, roughly triangular flakes, each measuring about 1 to 5 microns (millionths of a meter) across. They were grown atop titanium dioxide crystals using a conventional layering process known as chemical vapor deposition, and the defects were largely concentrated around the edges of the flakes, a signature of the growth process. Most of the experiments focused on a single flake of tungsten disulfide.

    2
    This image shows an illustration of the atomic structure of a 2D material called tungsten disulfide. Tungsten atoms are shown in blue and sulfur atoms are shown in yellow. The background image, taken by an electron microscope at Berkeley Lab’s Molecular Foundry, shows groupings of flakes of the material (dark gray) grown by a process called chemical vapor deposition on a titanium dioxide layer (light gray). (Credit: Katherine Cochrane/Berkeley Lab)

    Adam Schwartzberg, a staff scientist at the Molecular Foundry who served as a co-lead in the study, said, “It took a combination of multiple types of techniques to pin down what’s really going on.”

    He added, “Now that we know what defects we have and what effect they have on the properties of the material, we can use this information to reduce or eliminate defects – or if you want the defect, it gives us a way of knowing where the defects are,” and provides fresh insight about how to propagate and amplify the defects in the sample-production process.

    While the concentration of edge defects in the WS2 flakes was generally known before the latest study, Schwartzberg said that their effects on materials performance hadn’t previously been studied in such a comprehensive and detailed way.

    Researchers learned that a 10 percent deficiency in sulfur atoms was associated with the defective edge regions of the samples compared to other regions, and they identified a slighter, 3 percent sulfur deficiency toward the center of the flakes. Researchers also noted a change in the electronic structure and higher abundance of freely moving electrical charge-carriers associated with the high-defect edge areas.

    4
    This sequence of images shows a variety of energy intensities (white and yellow) at the edges of a 2D material known as tungsten disulfide, as measured via different techniques: photoluminescense intensity (far left); contact potential difference map (second from left); exciton emission intensity (third from left) – excitons are pairs consistent of an electrons and their quasiparticle counterpart, called a hole; trion emission intensity (far right) – trions are gropus of three charged quasiparticles consistening of either two electrons and a hole or two holes and an electron). (Credit: Christoph Kastl/Berkeley Lab)

    For this study, the defects were due to the sample-growth process. Future nanoARPES studies will focus on samples with defects that are induced through chemical processing or other treatments. Researchers hope to control the amount and kinds of atoms that are affected, and the locations where these defects are concentrated in the flakes.

    Such tiny tweaks could be important for processes like catalysis, which is used to enhance and accelerate many important industrial chemical production processes, and to explore quantum processes that rely on the production of individual particles that serve as information carriers in electronics.

    Because research of WS2 and related 2D materials is still in its infancy, there are many unknowns about the roles specific types of defects play in these materials, and Rotenberg noted that there is a world of possibilities for so-called “defect engineering” in these materials.

    In addition, MAESTRO’s nanoARPES has the ability to study the electronic structures of stacks of different types of 2D material layers. This can help researchers understand how their properties depend on their physical arrangement, and to explore working devices that incorporate 2D materials.

    “The unprecedented small scale of the measurements – currently approaching 50 nanometers – makes nanoARPES a great discovery tool that will be particularly useful to understand new materials as they are invented,” Rotenberg said.

    MAESTRO is one of the priority beamlines to be upgraded as part of the Lab’s ALS Upgrade (ALS-U) project, a major undertaking that will produce even brighter, more focused beams of light for experiments. “The ALS-U project will further improve the performance of the nanoARPES technique,” Rotenberg said, “making its measurements 10 to 30 times more efficient and significantly improving our ability to reach even shorter length scales.”

    NanoARPES could play an important role in the development of new solar technologies, because it allows researchers to see how nanoscale variations in chemical makeup, number of defects, and other structural features affect the electrons that ultimately govern their performance. These same issues are important for many other complex materials, such as superconductors, magnets, and thermoelectrics – which convert temperature to current and vice versa – so nanoARPES will also be very useful for these as well.

    The Molecular Foundry and ALS are both DOE Office of Science User Facilities.

    Researchers from the Berkeley Lab Chemical Sciences Division, Aarhus University in Denmark, and Montana State University also participated in this study. The work was supported by the U.S. Department of Energy’s Office of Basic Energy Sciences, the DOE Early Career Grant program, Berkeley Lab’s Laboratory Directed Research and Development program, the Villum Foundation, and the German Academic Exchange Service.

    See the full article here .

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    Please help promote STEM in your local schools.

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    Bringing Science Solutions to the World

    In the world of science, Lawrence Berkeley National Laboratory (Berkeley Lab) is synonymous with “excellence.” Thirteen Nobel prizes are associated with Berkeley Lab. Seventy Lab scientists are members of the National Academy of Sciences (NAS), one of the highest honors for a scientist in the United States. Thirteen of our scientists have won the National Medal of Science, our nation’s highest award for lifetime achievement in fields of scientific research. Eighteen of our engineers have been elected to the National Academy of Engineering, and three of our scientists have been elected into the Institute of Medicine. In addition, Berkeley Lab has trained thousands of university science and engineering students who are advancing technological innovations across the nation and around the world.

    Berkeley Lab is a member of the national laboratory system supported by the U.S. Department of Energy through its Office of Science. It is managed by the University of California (UC) and is charged with conducting unclassified research across a wide range of scientific disciplines. Located on a 202-acre site in the hills above the UC Berkeley campus that offers spectacular views of the San Francisco Bay, Berkeley Lab employs approximately 3,232 scientists, engineers and support staff. The Lab’s total costs for FY 2014 were $785 million. A recent study estimates the Laboratory’s overall economic impact through direct, indirect and induced spending on the nine counties that make up the San Francisco Bay Area to be nearly $700 million annually. The Lab was also responsible for creating 5,600 jobs locally and 12,000 nationally. The overall economic impact on the national economy is estimated at $1.6 billion a year. Technologies developed at Berkeley Lab have generated billions of dollars in revenues, and thousands of jobs. Savings as a result of Berkeley Lab developments in lighting and windows, and other energy-efficient technologies, have also been in the billions of dollars.

    Berkeley Lab was founded in 1931 by Ernest Orlando Lawrence, a UC Berkeley physicist who won the 1939 Nobel Prize in physics for his invention of the cyclotron, a circular particle accelerator that opened the door to high-energy physics. It was Lawrence’s belief that scientific research is best done through teams of individuals with different fields of expertise, working together. His teamwork concept is a Berkeley Lab legacy that continues today.

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

    University of California Seal

    DOE Seal

     
  • richardmitnick 4:19 pm on March 6, 2019 Permalink | Reply
    Tags: An atom-defect hybrid quantum system, , , Coherence in quantum behavior, If you can see things on smaller scales with better sensitivity than anybody else you’re going to find new physics, In the experiment we will have an atom on the diamond surface that couples to a shallow subsurface NV center inside the material in a highly controlled cryogenic and ultra-high vacuum environment, Key to this technology is the nitrogen-vacancy (NV) center in diamond an extensively studied point defect in diamond’s carbon atom lattice, Nanotechnology, , , , The physical and materials knowledge gained by mastering the interface of such a hybrid system would contribute to the development of quantum computing systems, The technique is reminiscent of molecular beam epitaxy (MBE) a method of “growing” a material atom-by-atom on a substrate, This project is a “natural fit” for UC Santa Barbara say the researchers due to the campus’s strengths in both physics and materials sciences, To Hold Without Touching, UCSB- University of California Santa Barbara   

    From UC Santa Barbara: “Sensing Disturbances in the Force” 

    UC Santa Barbara Name bloc
    From UC Santa Barbara

    March 5, 2019
    Sonia Fernandez

    UC Santa Barbara researchers receive U.S. Department of Energy grant to build atom-defect hybrid quantum sensor.

    1

    It will be a feat of engineering and physics at the smallest scales, but it could open the biggest doors — to new science and more advanced technologies. UC Santa Barbara physicists Ania Jayich and David Weld, and materials scientist Kunal Mukherjee, are teaming up to build an atom-defect hybrid quantum system — a sensor technology that would use the power of quantum science to unlock the mysteries of the atomic and subatomic world.

    “We’re at this tipping point where we know there’s a lot of impactful and fundamentally exciting things we can do,” said Jayich, whose research investigates quantum effects at the nanoscale. The $1.5 million grant from the Department of Energy’s Office of Basic Sciences will kickstart the development of a system that will allow researchers an unusually high level of control over atoms while simultaneously leaving their “quantumness” untouched.

    “In this whole field of quantum technology, that has been the big challenge,” Jayich said. In the quirky and highly unintuitive world of quantum mechanics, she explained, objects can exist in a superposition of many places at once, and entangled elements separated by thousands of miles can be inextricably linked — phenomena which, in turn, have opened up new and powerful possibilities for areas such as sensing, computing and the deepest investigations of nature.

    However, the coherence that is the signature of these quantum behaviors — a state of information that is the foundation of quantum technology — is exceedingly fragile and fleeting.

    “Quantum coherence is such a delicate phenomenon,” Jayich said. “Any uncontrolled interaction with the environment will kill it. And that’s the whole challenge behind advancing this field — how do we preserve the very delicate quantumness of an atom or defect, or anything?” To study a quantum element such as an atom, one would have to interrogate it, she explained, but the act of measuring can also destroy its quantum nature.

    To Hold Without Touching

    Fortunately, Jayich and colleagues see a way around this conundrum.

    “It’s a hybrid atomic- and solid-state system,” Jayich said. Key to this technology is the nitrogen-vacancy (NV) center in diamond, an extensively studied point defect in diamond’s carbon atom lattice. The NV center is comprised of a vacancy created by a missing carbon atom next to another vacancy that is substituted with a nitrogen atom. With its several unpaired electrons, it is highly sensitive to and interactive with external perturbations, such as the minute magnetic or electric fields that would occur in the presence of individual atoms of interest.

    “In the proposed experiment, we would have an atom on the diamond surface that couples to a shallow, subsurface NV center inside the material, in a highly controlled, cryogenic and ultra-high vacuum environment,” Jayich explained. The diamond surface provides a natural trapping that allows researchers to more easily hold the atom in place — a challenge for many quantum scientists who want to trap individual atoms. Further, upon reading the state of the defect, one could understand the quantum properties of the atom under interrogation — without touching the atom itself and destroying its coherence.

    Previous methods aimed at interrogating individual adatoms (adsorbed atoms) relied on passing current through the atoms and necessitated metal surfaces, both of which, according to Jayich, reduce quantum coherence times.

    “The past several decades of work in atomic physics have resulted in tools that allow exquisite quantum control of all degrees of freedom of atomic ensembles, but typically only when the atoms are gently held in a vacuum far away from all other matter,” added Weld. “This experiment seeks to extend this level of control into a much messier but also much more technologically relevant regime, by manipulating and sensing individual atoms that are chemically bonded to a solid surface.”

    With the hybrid system, Jayich said, it would be “very easy to talk to the NV center defect with light, and the atoms have the benefit of retaining quantum information for very long periods of time. So we have a system where we leverage the best of both worlds — the best of the atom and the best of the defect — and put them together in a way that’s functional.”

    A Foundation for Future Quantum Tech

    Looking forward, the state-of-the-art spatial resolution and sensitivity of this atom-defect hybrid quantum system could offer researchers the deepest look at the workings of individual atoms, or structures of molecules at nanometer- and Angstrom scales.

    “If you can see things on smaller scales with better sensitivity than anybody else, you’re going to find new physics,” Jayich said. The connections of microscopic structure to macroscopic behavior in materials synthesis could be elucidated. Quantum phenomena in condensed matter systems could be probed. Proteins that have evaded structural determination — such as membrane proteins — could be studied.

    This project is a “natural fit” for UC Santa Barbara, say the researchers, due to the campus’s strengths in both physics and materials sciences. The technique is reminiscent of molecular beam epitaxy (MBE), a method of “growing” a material atom-by-atom on a substrate.

    “There is a strong tradition of materials deposition at UCSB, ranging from metals, semiconductors to novel electronic materials,” Mukherjee said of the campus’s long record of materials growth and world-class MBE facilities. Among the first few atoms they intend to study are rare-earth types such as holmium or dysprosium “as they have unpaired electrons which are protected from environmental interactions by the atomic structure,” noted Mukherjee, adding that he is “particularly excited” about the challenge of removing the atoms from and resetting the diamond surface without breaking vacuum.

    Additionally, the physical and materials knowledge gained by mastering the interface of such a hybrid system would contribute to the development of quantum computing systems. According to Jayich, future practicable quantum computers would likely be a hybrid of several elements, similar to how conventional computers are a mix of magnetic, electronic and solid-state components.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    UC Santa Barbara Seal
    The University of California, Santa Barbara (commonly referred to as UC Santa Barbara or UCSB) is a public research university and one of the 10 general campuses of the University of California system. Founded in 1891 as an independent teachers’ college, UCSB joined the University of California system in 1944 and is the third-oldest general-education campus in the system. The university is a comprehensive doctoral university and is organized into five colleges offering 87 undergraduate degrees and 55 graduate degrees. In 2012, UCSB was ranked 41st among “National Universities” and 10th among public universities by U.S. News & World Report. UCSB houses twelve national research centers, including the renowned Kavli Institute for Theoretical Physics.

     
  • richardmitnick 3:59 pm on March 4, 2019 Permalink | Reply
    Tags: A nanoworld on a chip, , “Ice rules” a principle that governs how atoms arrange themselves in ice formed from water or the mineral pyrochlore, , Berkeley Lab-led study could lead to smaller memory devices microelectronics and spintronics, , , Nanotechnology, PEEM-X-ray photoemission electron microscopy   

    From Lawrence Berkeley National Lab: “How to Catch a Magnetic Monopole in the Act” 

    Berkeley Logo

    From Lawrence Berkeley National Lab

    March 4, 2019
    Theresa Duque
    tnduque@lbl.gov
    (510) 495-2418

    Berkeley Lab-led study could lead to smaller memory devices, microelectronics, and spintronics

    1
    Magnetic monopoles in motion at 210 K. Red dots represent positive magnetic charges (north poles), while blue dots represent negative magnetic charges (south poles). (Credit: Farhan/Berkeley Lab)

    A research team led by the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) has created a nanoscale “playground” on a chip that simulates the formation of exotic magnetic particles called monopoles. The study – published recently in Science Advances – could unlock the secrets to ever-smaller, more powerful memory devices, microelectronics, and next-generation hard drives that employ the power of magnetic spin to store data.

    Follow the ‘ice rules’

    For years, other researchers have been trying to create a real-world model of a magnetic monopole – a theoretical magnetic, subatomic particle that has a single north or south pole. These elusive particles can be simulated and observed by manufacturing artificial spin ice materials – large arrays of nanomagnets that have structures analogous to water ice – wherein the arrangement of atoms isn’t perfectly symmetrical, leading to residual north or south poles.

    2
    This nanoscale “playground” on a chip uses nanomagnets to simulate the formation of exotic magnetic particles called “monopoles.” (Credit: Farhan/Berkeley Lab)

    Opposites attract in magnetism (north poles are drawn to south poles, and vice-versa) so these single poles attempt to move to find their perfect match. But because conventional artificial spin ices are 2D systems, the monopoles are highly confined, and are therefore not realistic representations of how magnetic monopoles behave, said lead author Alan Farhan, who was a postdoctoral fellow at Berkeley Lab’s Advanced Light Source (ALS) at the time of the study, and is now with the Paul Scherrer Institute in Switzerland.

    LBL ALS

    To overcome this obstacle, the Berkeley Lab-led team simulated a nanoscale 3D system that follows “ice rules,” a principle that governs how atoms arrange themselves in ice formed from water or the mineral pyrochlore.

    “This is a crucial element of our work,” said Farhan. “With our 3D system, a north monopole or south monopole can move wherever it wants to go, interacting with other particles in its environment like an isolated magnetic charge would – in other words, like a monopole.”

    A nanoworld on a chip

    4
    This XMCD (X-ray magnetic circular dichroism) image sequence recorded at 190 K shows how monopoles might form and move in response to changes in temperature. (Credit: Farhan/Berkeley Lab)

    The team used sophisticated lithography tools developed at Berkeley Lab’s Molecular Foundry, a nanoscale science research facility, to pattern a 3D, square lattice of nanomagnets. Each magnet in the lattice is about the size of a bacterium and rests on a flat, 1-by-1-centimeter silicon wafer.

    LBNL Molecular Foundry

    “It’s a nanoworld – with tiny architecture on a tiny wafer,” but atomically configured exactly like natural ice, said Farhan.

    To build the nanostructure, the researchers synthesized two exposures, each one aligned within 20 to 30 nanometers. At the Molecular Foundry, co-author Scott Dhuey fabricated nanopatterns of four types of structures onto a tiny silicon chip. The chips were then studied at the ALS, a synchrotron light source research facility open to visiting scientists from around the world. The researchers used a technique called X-ray photoemission electron microscopy (PEEM), directing powerful beams of X-ray light sensitive to magnetic structures at the nanopatterns to observe how monopoles might form and move in response to changes in temperature.

    In contrast to PEEM microscopes at other light sources, Berkeley Lab’s PEEM3 microscope has a higher X-ray angle of incidence, minimizing shadow effects – which are similar to the shadows cast by a building when the sun strikes the surface at a certain angle. “In fact, the images recorded reveal no shadow effect whatsoever,” said Farhan. “This makes the PEEM3 the most crucial element to this project’s success.”

    Farhan added that the PEEM3 is the only microscope in the world that gives users full temperature control in the sub-100 Kelvin (below minus 280 degrees Fahrenheit) range, capturing in real time how emergent magnetic monopoles form as artificial frozen ice melts into a liquid, and as liquid evaporates into a gas-like state of magnetic charges – a form of matter known as plasma.

    The researchers now hope to pattern smaller and smaller nanomagnets for the advancement of smaller yet more powerful spintronics – a sought-after field of microelectronics that taps into particles’ magnetic spin properties to store more data in smaller devices such as magnetic hard drives.

    Such devices would use magnetic films and superconducting thin films to deploy and manipulate magnetic monopoles to sort and store data based on the north or south direction of their poles – analogous to the ones and zeros in conventional magnetic storage devices.

    The ALS and the Molecular Foundry are DOE Office of Science user facilities.

    The work research was supported by the U.S. Department of Energy’s Office of Science, and the Swiss National Science Foundation.

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    Bringing Science Solutions to the World

    In the world of science, Lawrence Berkeley National Laboratory (Berkeley Lab) is synonymous with “excellence.” Thirteen Nobel prizes are associated with Berkeley Lab. Seventy Lab scientists are members of the National Academy of Sciences (NAS), one of the highest honors for a scientist in the United States. Thirteen of our scientists have won the National Medal of Science, our nation’s highest award for lifetime achievement in fields of scientific research. Eighteen of our engineers have been elected to the National Academy of Engineering, and three of our scientists have been elected into the Institute of Medicine. In addition, Berkeley Lab has trained thousands of university science and engineering students who are advancing technological innovations across the nation and around the world.

    Berkeley Lab is a member of the national laboratory system supported by the U.S. Department of Energy through its Office of Science. It is managed by the University of California (UC) and is charged with conducting unclassified research across a wide range of scientific disciplines. Located on a 202-acre site in the hills above the UC Berkeley campus that offers spectacular views of the San Francisco Bay, Berkeley Lab employs approximately 3,232 scientists, engineers and support staff. The Lab’s total costs for FY 2014 were $785 million. A recent study estimates the Laboratory’s overall economic impact through direct, indirect and induced spending on the nine counties that make up the San Francisco Bay Area to be nearly $700 million annually. The Lab was also responsible for creating 5,600 jobs locally and 12,000 nationally. The overall economic impact on the national economy is estimated at $1.6 billion a year. Technologies developed at Berkeley Lab have generated billions of dollars in revenues, and thousands of jobs. Savings as a result of Berkeley Lab developments in lighting and windows, and other energy-efficient technologies, have also been in the billions of dollars.

    Berkeley Lab was founded in 1931 by Ernest Orlando Lawrence, a UC Berkeley physicist who won the 1939 Nobel Prize in physics for his invention of the cyclotron, a circular particle accelerator that opened the door to high-energy physics. It was Lawrence’s belief that scientific research is best done through teams of individuals with different fields of expertise, working together. His teamwork concept is a Berkeley Lab legacy that continues today.

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

    University of California Seal

    DOE Seal

     
  • richardmitnick 10:28 am on March 4, 2019 Permalink | Reply
    Tags: , , , Directed evolution, Engineer synthetic nanoparticles as optical biosensors, , Nanotechnology,   

    From École Polytechnique Fédérale de Lausanne: “Directed evolution builds nanoparticles” 

    EPFL bloc

    From École Polytechnique Fédérale de Lausanne

    3.3.19
    Nik Papageorgiou

    1
    Directed evolution is a powerful technique for engineering proteins. EPFL scientists now show that it can also be used to engineer synthetic nanoparticles as optical biosensors, which are used widely in biology, drug development, and even medical diagnostics such as real-time monitoring of glucose.

    The 2018 Nobel Prize in Chemistry went to three scientists who developed the method that forever changed protein engineering: directed evolution. Mimicking natural evolution, directed evolution guides the synthesis of proteins with improved or new functions.

    First, the original protein is mutated to create a collection of mutant protein variants. The protein variants that show improved or more desirable functions are selected. These selected proteins are then once more mutated to create another collection of protein variants for another round of selection. This cycle is repeated until a final, mutated protein is evolved with optimized performance compared to the original protein.

    Now, scientists from the lab of Ardemis Boghossian at EPFL, have been able to use directed evolution to build not proteins, but synthetic nanoparticles. These nanoparticles are used as optical biosensors – tiny devices that use light to detect biological molecules in air, water, or blood. Optical biosensors are widely used in biological research, drug development, and medical diagnostics, such as real-time monitoring of insulin and glucose in diabetics.

    “The beauty of directed evolution is that we can engineer a protein without even knowing how its structure is related to its function,” says Boghossian. “And we don’t even have this information for the vast, vast majority of proteins.”

    Her group used directed evolution to modify the optoelectronic properties of DNA-wrapped single-walled carbon nanotubes (or, DNA-SWCNTs, as they are abbreviated), which are nano-sized tubes of carbon atoms that resemble rolled up sheets of graphene covered by DNA. When they detect their target, the DNA-SWCNTs emit an optical signal that can penetrate through complex biological fluids, like blood or urine.

    2
    General principle of the directed evolution approach applied to the nanoparticle DNA-SWCNT complexes. The starting complex is a DNA-SWCNT with a dim optical signal. This is evolved through directed evolution: (1) random mutation of the DNA sequence; (2) wrapping of the SWCNTs with the DNA and screening of the complex’s optical signal; (3) selection of the DNA-SWCNT complexes exhibiting an improved optical signal. After several cycles of evolution, we can evolve DNA-SWCNT complexes that show enhanced optical behavior. Credit: Benjamin Lambert (EPFL)

    Using a directed evolution approach, Boghossian’s team was able to engineer new DNA-SWCNTs with optical signals that are increased by up to 56% – and they did it over only two evolution cycles.

    “The majority of researchers in this field just screen large libraries of different materials in hopes of finding one with the properties they are looking for,” says Boghossian. “In optical nanosensors, we try to improve properties like selectivity, brightness, and sensitivity. By applying directed evolution, we provide researchers with a guided approach to engineering these nanosensors.”

    The study [Chemical Communications] shows that what is essentially a bioengineering technique can be used to more rationally tune the optoelectronic properties of certain nanomaterials. Boghossian explains: “Fields like materials science and physics are mostly preoccupied with defining material structure-function relationships, making materials that lack this information difficult to engineer. But this is a problem that nature solved billions of years ago – and, in recent decades, biologists have tackled it as well. I think our study shows that as materials scientists and physicists, we can still learn a few pragmatic lessons from biologists.”
    Funding

    SNSF AP Energy Grant

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    EPFL campus

    EPFL is Europe’s most cosmopolitan technical university. It receives students, professors and staff from over 120 nationalities. With both a Swiss and international calling, it is therefore guided by a constant wish to open up; its missions of teaching, research and partnership impact various circles: universities and engineering schools, developing and emerging countries, secondary schools and gymnasiums, industry and economy, political circles and the general public.

     
  • richardmitnick 4:07 pm on February 24, 2019 Permalink | Reply
    Tags: "Researchers use ‘laser tweezers’ to boost liquid crystal technology", , , , Liquid crystals with their uniform molecular structure and orientation offer exciting possibilities for future technology, Nanotechnology, To create the defects in the liquid crystals researchers used laser tweezers—a laser system that can manipulate particles at the nanoscale—to heat up and melt either a tiny point or a line within , , We can keep the defect alive for as long as we want   

    From University of Chicago: “Researchers use ‘laser tweezers’ to boost liquid crystal technology” 

    U Chicago bloc

    From University of Chicago

    Feb 22, 2019
    Emily Ayshford

    1
    Illustration copyright Wikimedia Commons

    Institute for Molecular Engineering breakthrough could lead to new display or sensor technologies.

    Liquid crystals, with their uniform molecular structure and orientation, offer exciting possibilities for future technology.

    They are already the basis of displays, which use the crystals’ orientation to exhibit a wide array of colors. Researchers have wondered whether they could manipulate tiny defects in the crystals to introduce new functions within the liquid—as microchannels for a tiny circuit, or to host chemical reactions, for example. But the first step is to keep the defects stable.

    Researchers with the Institute for Molecular Engineering at the University of Chicago, along with partners at the University of Ljubljana, have shown that by using a combination of flow and light, they can create defects that remain stable in the liquid crystal over long periods of time. The breakthrough, published Feb. 15 in the journal Science Advances, could ultimately result in using liquids in new ways, such as to create new kinds of autonomous materials or nanoscale reactors.

    “For the first time, we can create defects in pure liquids and control them, without introducing anything else into the system,” said Juan de Pablo, the Liew Family Professor in Molecular Engineering at the University of Chicago, who co-authored the research. “It could result in really interesting new objects or materials.”

    To create the defects in the liquid crystals, researchers used laser tweezers—a laser system that can manipulate particles at the nanoscale—to heat up and melt either a tiny point or a line within the material. While the bulk of the liquid crystal remained ordered, the melted spot — several microns in size, just a little smaller than a single red blood cell—became disorganized. As it cooled, the molten liquid becomes reordered, and forms a defect on its trail.

    Because such defects cost the material energy, the material experiences strong driving forces to eliminate them, and it eventually reverts to a uniform, defect-free state.

    But researchers found that if they place the defect into a flow state in a microfluidic device—introducing forces that continually push the defect in different directions—it could not reorient and annihilate itself, and instead remained stable.

    “By doing this, we can keep the defect alive for as long as we want,” said de Pablo, whose pioneering work develops molecular models and advanced computational simulations of molecular and large-scale phenomena.

    Such a system also allowed them to have complete control over the size and shape of the defects. A second laser burst, for example, could break the defect into pieces, or move it from one spot to another.

    To create this system, de Pablo and his group developed computational models of liquid crystals at rest, their defects and the precise forces needed to keep them stabilized. Then the researchers at the University of Ljubljana performed the experiments using this information and theoretical treatments of the underlying materials.

    This system could pave the way for new display or sensor technologies. De Pablo and his collaborators are interested in using this technique to develop complicated networks of microfluidic channels that could serve as miniature factories, with built-in reactors, separation units and transport mechanisms.

    They also are looking to develop autonomous material systems that can stabilize defects on their own using flows. Such a material could “decide” by itself what shape to take in response to external cues, ultimately acting as an integrated system that could perform simple tasks on its own.

    “This technique could have really interesting applications,” de Pablo said. “We have ambitious ideas.”

    Other authors included Rui Zhang, a postdoctoral researcher in de Pablo’s group; and Uroš Tkalec, Tadej Emeršič, Žiga Kos, Simon Čopar and Natan Osterman of the University of Ljubljana.

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    U Chicago Campus

    An intellectual destination

    One of the world’s premier academic and research institutions, the University of Chicago has driven new ways of thinking since our 1890 founding. Today, UChicago is an intellectual destination that draws inspired scholars to our Hyde Park and international campuses, keeping UChicago at the nexus of ideas that challenge and change the world.

    University of Chicago

    The University of Chicago is an urban research university that has driven new ways of thinking since 1890. Our commitment to free and open inquiry draws inspired scholars to our global campuses, where ideas are born that challenge and change the world.

    We empower individuals to challenge conventional thinking in pursuit of original ideas. Students in the College develop critical, analytic, and writing skills in our rigorous, interdisciplinary core curriculum. Through graduate programs, students test their ideas with UChicago scholars, and become the next generation of leaders in academia, industry, nonprofits, and government.

    UChicago research has led to such breakthroughs as discovering the link between cancer and genetics, establishing revolutionary theories of economics, and developing tools to produce reliably excellent urban schooling. We generate new insights for the benefit of present and future generations with our national and affiliated laboratories: Argonne National Laboratory, Fermi National Accelerator Laboratory, and the Marine Biological Laboratory in Woods Hole, Massachusetts.

    The University of Chicago is enriched by the city we call home. In partnership with our neighbors, we invest in Chicago’s mid-South Side across such areas as health, education, economic growth, and the arts. Together with our medical center, we are the largest private employer on the South Side.

    In all we do, we are driven to dig deeper, push further, and ask bigger questions—and to leverage our knowledge to enrich all human life. Our diverse and creative students and alumni drive innovation, lead international conversations, and make masterpieces. Alumni and faculty, lecturers and postdocs go on to become Nobel laureates, CEOs, university presidents, attorneys general, literary giants, and astronauts.

     
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