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  • richardmitnick 9:43 am on March 25, 2019 Permalink | Reply
    Tags: "In a new quantum simulator light behaves like a magnet", , EPFL-École Polytechnique Fédérale de Lausanne, , ,   

    From École Polytechnique Fédérale de Lausanne: “In a new quantum simulator, light behaves like a magnet” 

    EPFL bloc

    From École Polytechnique Fédérale de Lausanne

    3.25.19
    Nik Papageorgiou

    1
    Physicists at EPFL propose a new “quantum simulator”: a laser-based device that can be used to study a wide range of quantum systems. Studying it, the researchers have found that photons can behave like magnetic dipoles at temperatures close to absolute zero, following the laws of quantum mechanics. The simple simulator can be used to better understand the properties of complex materials under such extreme conditions.

    When subject to the laws of quantum mechanics, systems made of many interacting particles can display behaviour so complex that its quantitative description defies the capabilities of the most powerful computers in the world. In 1981, the visionary physicist Richard Feynman argued we can simulate such complex behavior using an artificial apparatus governed by the very same quantum laws – what has come to be known as a “quantum simulator”.

    One example of a complex quantum system is that of magnets placed at really low temperatures. Close to absolute zero (-273.15°C), magnetic materials may undergo what is known as a “quantum phase transition”. Like a conventional phase transition (e.g. ice melting into water, or water evaporating into steam), the system still switches between two states, except that close to the transition point the system manifests quantum entanglement – the most profound feature predicted by quantum mechanics. Studying this phenomenon in real materials is an astoundingly challenging task for experimental physicists.

    But physicists led by Vincenzo Savona at EPFL have now come up with a quantum simulator that promises to solve the problem. “The simulator is a simple photonic device that can easily be built and run with current experimental techniques,” says Riccardo Rota, the postdoc at Savona’s lab who led the study. “But more importantly, it can simulate the complex behavior of real, interacting magnets at very low temperatures.”

    The simulator may be built using superconducting circuits – the same technological platform used in modern quantum computers. The circuits are coupled to laser fields in such a way that it causes an effective interaction among light particles (photons). “When we studied the simulator, we found that the photons behaved in the same way as magnetic dipoles across the quantum phase transition in real materials,” says Rota. In short, we can now use photons to run a virtual experiment on quantum magnets instead of having to set up the experiment itself.

    “We are theorists,” says Savona. “We came up with the idea for this particular quantum simulator and modelled its behavior using traditional computer simulations, which can be done when the quantum simulator addresses a small enough system. Our findings prove that the quantum simulator we propose is viable, and we are now in talks with experimental groups who would like to actually build and use it.”

    Understandably, Rota is excited: “Our simulator can be applied to a broad class of quantum systems, allowing physicists to study several complex quantum phenomena. It is a truly remarkable advance in the development of quantum technologies.”

    Science paper:
    Riccardo Rota, Fabrizio Minganti, Cristiano Ciuti, Vincenzo Savona.
    “Quantum Critical Regime in a Quadratically Driven Nonlinear Photonic Lattice”
    Physical Review Letters

    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 10:28 am on March 4, 2019 Permalink | Reply
    Tags: , , , Directed evolution, Engineer synthetic nanoparticles as optical biosensors, EPFL-École Polytechnique Fédérale de Lausanne, ,   

    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 12:46 pm on February 20, 2019 Permalink | Reply
    Tags: , EPFL-École Polytechnique Fédérale de Lausanne, ,   

    From École Polytechnique Fédérale de Lausanne: “The holy grail of nanowire production” 

    EPFL bloc

    From École Polytechnique Fédérale de Lausanne

    2.20.19
    Laure-Anne Pessina

    1
    EPFL researchers have found a way to control and standardize the production of nanowires on silicon surfaces. This discovery could make it possible to grow nanowires on electronic platforms, with potential applications including the integration of nanolasers into electronic chips and improved energy conversion in solar panels.

    Nanowires have the potential to revolutionize the technology around us. Measuring just 5-100 nanometers in diameter (a nanometer is a millionth of a millimeter), these tiny, needle-shaped crystalline structures can alter how electricity or light passes through them.

    They can emit, concentrate and absorb light and could therefore be used to add optical functionalities to electronic chips. They could, for example, make it possible to generate lasers directly on silicon chips and to integrate single-photon emitters for coding purposes. They could even be applied in solar panels to improve how sunlight is converted into electrical energy.

    Up until now, it was impossible to reproduce the process of growing nanowires on silicon semiconductors – there was no way to repeatedly produce homogeneous nanowires in specific positions. But researchers from EPFL’s Laboratory of Semiconductor Materials, run by Anna Fontcuberta i Morral, together with colleagues from MIT and the IOFFE Institute, have come up with a way of growing nanowire networks in a highly controlled and fully reproducible manner. The key was to understand what happens at the onset of nanowire growth, which goes against currently accepted theories. Their work has been published in Nature Communications.

    2
    Two different configurations of the droplet within the opening – hole fully filled and partially filled and bellow illustration of GaAs crystals forming a full ring or a step underneath the large and small gallium droplets.

    “We think that this discovery will make it possible to realistically integrate a series of nanowires on silicon substrates,” says Fontcuberta i Morral. “Up to now, these nanowires had to be grown individually, and the process couldn’t be reproduced.”

    Getting the right ratio

    The standard process for producing nanowires is to make tiny holes in silicon monoxide and fill them with a nanodrop of liquid gallium. This substance then solidifies when it comes into contact with arsenic. But with this process, the substance tends to harden at the corners of the nanoholes, which means that the angle at which the nanowires will grow can’t be predicted. The search was on for a way to produce homogeneous nanowires and control their position.

    Research aimed at controlling the production process has tended to focus on the diameter of the hole, but this approach has not paid off. Now EPFL researchers have shown that by altering the diameter-to-height ratio of the hole, they can perfectly control how the nanowires grow. At the right ratio, the substance will solidify in a ring around the edge of the hole, which prevents the nanowires from growing at a non-perpendicular angle. And the researchers’ process should work for all types of nanowires.

    “It’s kind of like growing a plant. They need water and sunlight, but you have to get the quantities right,” says Fontcuberta i Morral.

    This new production technique will be a boon for nanowire research, and further samples should soon be developed.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    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 11:57 am on November 7, 2018 Permalink | Reply
    Tags: , EPFL-École Polytechnique Fédérale de Lausanne, , Remote recharging system   

    From École Polytechnique Fédérale de Lausanne: “Using diamonds to recharge civilian drones in flight” 

    EPFL bloc

    From École Polytechnique Fédérale de Lausanne

    07.11.18
    Cécilia Carron

    1
    Un système de laser pourrait permettre de recharger des drones en vol grâce à un diamant industriel© 2018 Jamani Caillet

    2
    © 2018 LakeDiamond

    A small lab-grown diamond measuring a few millimeters per side could one day enable civilian drones to be recharged in mid-flight through a laser. Thanks to the diamond, the laser beam can remain strong enough over a long distance to recharge photovoltaic cells on the drones’ surface. This system, which poses no threat to human health, is being developed by EPFL spin-off LakeDiamond. It could also be used to transmit both power and data to satellites and has just been included in the ten projects supported for two years by of the Swiss Space Office.

    Drones are being used for a growing number of purposes. Their designs are ever more efficient, and techniques for flying them are being further refined all the time. But drones still have the same weak point: their battery. This is particularly true of propeller drones, which are popular for information-gathering purposes in dangerous or hard-to-reach regions. These drones can fly for only around 15 minutes at a time because their engines quickly burn through their batteries. One way of addressing this limitation – without weighing the drones down – would be to recharge them while aloft using a power beaming system: an energy-rich laser beam that is guided by a tracking system and shines directly on photovoltaic cells on the drones’ exterior.

    Several labs around the world, including in the US, have been working on this idea in recent years. LakeDiamond, an EPFL spin-off based at Innovation Park, has now demonstrated the feasibility of using a high-power laser for this purpose. What’s more, LakeDiamond’s laser emits a wavelength that cannot damage human skin or eyes – the issue of safety is paramount, since the system is meant for use with civilian drones. LakeDiamond’s technology is built around diamonds that are grown in the company’s lab and subsequently etched at the atomic level.

    World record for power

    Despite appearances, standard laser beams are not as straight as they seem: as they travel, they expand ever so slightly, leading to a loss in density as they go. But LakeDiamond’s system produces a laser beam with a wavelength of 1.5 µm that, in addition to being safe, can travel much farther without losing strength. “Systems developed by other companies and labs, often for military applications, employ lasers that are more powerful and thus more dangerous for humans,” says Pascal Gallo, CEO of LakeDiamond. His company took the opposite tack: their technology transforms the rays emitted by a simple low-power diode into a high-quality laser beam. Their beam has a larger diameter, and its rays remain parallel over a longer distance – in this case up to several hundred meters.

    In LakeDiamond’s laser, the light produced by a diode is directed at a booster composed of reflective material, an optical component and a small metal plate to absorb the heat. The breakthrough lies not with this set-up, which already exists, but with the fact that the emitted beam is only a few dozen watts strong. The secret is using a small square lab-grown diamond as the optical component, as this delivers unparalleled performance. LakeDiamond’s system holds the world record for continuous operation using a wavelength in the middle of the infrared range – it delivers more than 30 watts in its base configuration. “That’s equivalent to around 10,000 laser pointers,” adds Gallo.

    The lab-grown diamonds’ key properties include high transparency and thermal conductivity. Achieving those things – and mastering the nano-etching process – took the researchers over ten years of development. LakeDiamond grows its diamonds through a process of chemical vapor deposition, an approach that ensures their purity and reproducibility. The surfaces of the resulting tiny square diamonds are then sculpted at the nano level using expertise developed in Niels Quack’s lab at EPFL (read the EPFL article on this topic). Thanks to their inherent properties and etched shapes, the diamonds are able to transfer heat to a small metal plate that dissipates it, while at the same time reflecting light in such a way as to create a laser beam.

    “To achieve greater power – say to recharge a larger drone – these lasers could easily be operated in series,” says Nicolas Malpiece, who is in charge of power beaming at LakeDiamond. The company’s remote recharging system works in the lab but will require further development and refinement before it’s ready for field use. What would happen if a drone flies behind an obstacle and is cut off from its laser energy source? Several approaches to this problem are currently being explored. A small back-up battery could take over temporarily, or, for information-gathering missions over rough terrain for example, the drone could simply return to within range of the laser in order to top up its battery.

    This energy transmission system is also interesting for other areas of application. It can for example be used for charging and transmitting data to satellites. The development of the system is included in a support program of the Swiss Space Office, which began on 1 November and runs for two years.

    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 11:12 am on November 7, 2018 Permalink | Reply
    Tags: EPFL-École Polytechnique Fédérale de Lausanne, , The Technion joins EuroTech Universities Alliance   

    From École Polytechnique Fédérale de Lausanne: “The Technion joins EuroTech Universities Alliance” 

    EPFL bloc

    From École Polytechnique Fédérale de Lausanne

    07.11.18
    EuroTech communications

    The Technion campus on Mount Carmel in Haïfa. DR

    Technion, Israel Institute of Technology, will join the EuroTech Universities Alliance as of 1 January 2019. Made public on the occasion of the Alliance’s annual High Level Event in Brussels on 6 November, the announcement follows the accession of France’s École Polytechnique to the Alliance in June 2018. This step increase in the Alliance’s membership base – composed also of EPFL, TU Eindhoven (Netherlands), DTU (Danemark) and TUM (Germany) and will further strengthen its position as pioneer for inter-university collaboration.

    “The EuroTech Universities are excellent research-based universities recognized within their innovation eco-systems as highly dynamic motors with an outstanding capacity to help translate basic research into societal solutions”, says Jan Mengelers, President of the EuroTech Universities Alliance. “With the EuroTech Universities Alliance, we are pooling our complementary research strengths and connecting our innovation eco-systems for more impact. Technion is a “perfect match” to join – and boost this joint endeavour, given its scientific excellence and vibrant innovation ecosystem.”

    Boasting 84 ERC grants under the EU’s FP7 and Horizon 2020 programmes as well as 90 spin-off companies, Technion is a striking example of how excellent fundamental science translates into impact. “Technion is thrilled and honoured to join the EuroTech Universities Alliance”, says Technion President, Prof. Peretz Lavie. “We live in an era in which international and interdisciplinary collaborations are vital to the future of scientific research. We bring the ‘Technion way’ of doing things to this partnership: reaching our goals faster and with less resources. The combination with the great strengths of the other members of the alliance, which comprises an elite group of European universities similar to Technion, will help us ensure we are at the forefront of scientific research, benefiting millions worldwide.“

    The EuroTech Universities Alliance stimulates collaboration across education, research and innovation, thereby increasing the attraction of global top talent needed to drive modernization, excellence and societal impact. For instance, the existing EuroTech Postdoc programme[1] provides 80 promising fellows unique access to the research expertise and infrastructures across the EuroTech Universities while at the same time offering exclusive entrepreneurship and mobility opportunities in several of Europe’s top high-tech eco-systems.

    Today’s societal challenges can only be addressed by collaboration in education, research and innovation across the EU and internationally. Recognizing what alliances of universities can achieve when pooling resources and combining strengths, the European Commission launched a pilot scheme in support of European university networks on 24 October 2018. At its annual High-Level Event in Brussels on 6 November, the EuroTech Universities Alliance facilitated a very timely and encouraging debate on the role of university alliances in driving the ‘University of the Future’.

    [1] EuroTech Postdoc is one of the first cross-country fellowship programmes co-funded by the EU’s Horizon 2020 research and innovation programme (MSCA grant agreement Nr 754462). Its second call will be published on the Programme Website on 30 November 2018.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    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 9:28 am on November 5, 2018 Permalink | Reply
    Tags: EPFL-École Polytechnique Fédérale de Lausanne, MOFs-Metallic Organic Frameworks, New material cleans and splits water, Organic pollutant degradation,   

    From École Polytechnique Fédérale de Lausanne: “New material cleans and splits water” 

    EPFL bloc

    From École Polytechnique Fédérale de Lausanne

    05.11.18
    Nik Papageorgiou

    1
    Simultaneous photocatalytic hydrogen generation and dye degradation using a visible light active metal–organic framework. Creidt: Alina-Stavroula Kampouri/EPFL

    Researchers at EPFL’s Institute of Chemical Sciences and Engineering have developed a photocatalytic system based on a material in the class of metal-organic frameworks. The system can be used to degrade pollutants present in water while simultaneously producing hydrogen that can be captured and used further.

    Some of the most useful and versatile materials today are the metal-organic frameworks (MOFs). MOFs are a class of materials demonstrating structural versatility, high porosity, fascinating optical and electronic properties, all of which makes them promising candidates for a variety of applications, including gas capture and separation, sensors, and photocatalysis.

    Because MOFs are so versatile in both their structural design and usefulness, material scientists are currently testing them in a number of chemical applications. One of these is photocatalysis, a process where a light-sensitive material is excited with light. The absorbed excess energy dislocates electrons from their atomic orbits, leaving behind “electron holes”. The generation of such electron-hole pairs is a crucial process in any light-dependent energy process, and, in this case, it allows the MOF to affect a variety of chemical reactions.

    A team of scientists at EPFL Sion led by Kyriakos Stylianou at the Laboratory of Molecular Simulation, have now developed a MOF-based system that can perform not one, but two types of photocatalysis simultaneously: production of hydrogen, and cleaning pollutants out of water. The material contains the abundantly available and cheap nickel phosphide (Ni2P), and was found to carry out efficient photocatalysis under visible light, which accounts to 44% of the solar spectrum.

    The first type of photocatalysis, hydrogen production, involves a reaction called “water-splitting”. Like the name suggests, the reaction divides water molecules into their constituents: hydrogen and oxygen. One of the bigger applications here is to use the hydrogen for fuel cells, which are energy-supply devices used in a variety of technologies today, including satellites and space shuttles.

    The second type of photocatalysis is referred to as “organic pollutant degradation”, which refers to processes breaking down pollutants present in water. The scientists investigated this innovative MOF-based photocatalytic system towards the degradation of the toxic dye rhodamine B, commonly used to simulate organic pollutants.

    The scientists performed both tests in sequence, showing that the MOF-based photocatalytic system was able to integrate the photocatalytic generation of hydrogen with the degradation of rhodamine B in a single process. This means that it is now possible to use this photocatalytic system to both clean pollutants out of water, while simultaneously producing hydrogen that can be used as a fuel.

    “This noble-metal free photocatalytic system brings the field of photocatalysis a step closer to practical ‘solar-driven’ applications and showcases the great potential of MOFs in this field,” says Kyriakos Stylianou.

    Other contributors

    University College London

    Science paper:
    Concurrent Photocatalytic Hydrogen Generation and Dye Degradation Using MIL‐125‐NH2 under Visible Light Irradiation
    Advanced Functional Materials

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    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 10:12 am on October 8, 2018 Permalink | Reply
    Tags: , , , , EPFL-École Polytechnique Fédérale de Lausanne, Near-field cosmology-studying stars of different generations allows us to understand the formation history of the Galaxy, Pristine 221, Pristine survey, The more pristine the atmosphere the earlier the generation in which this star was born   

    From École Polytechnique Fédérale de Lausanne and IAC: “A rare star opens a window on the beginning of time” 

    EPFL bloc

    From École Polytechnique Fédérale de Lausanne

    08.10.18
    Sarah Perrin, with AIP

    1
    Dedicated to the search of the most ancient stars in the Milky Way, the Pristine survey recently identified an extremely rare object. ©iStock

    EPFL astrophysicists actively participated in the discovery of a very rare star, which is particularly old and metal-poor. As a messenger from the distant past, it will allow the scientists to learn more about the young Universe, right after the Big Bang.

    2

    “We made a major discovery, which questions our understanding of the formation of the first generations of stars in the universe”. Researcher at EPFL Laboratory of astrophysics (LASTRO), Pascale Jablonka is a founding member of the Pristine survey, an international project dedicated to the search of the most ancient and metal-poor stars. It allowed the recent identification of an extremely rare object. Called Pristine 221, it is among the 10 most metal-poor stars known to date in the halo of our Galaxy. Moreover, it is one out of two outstanding stars that are almost totally carbon free. This breakthrough has recently been published in the journal Monthly Notices of the Royal Astronomical Society (MNRAS).

    For the study of the early universe, astronomers have different methods at their disposal: One is to look far into the Universe and back in time, to see the first stars and galaxies growing. Another option is to examine the oldest surviving stars of our home galaxy, the Milky Way, for information from the early universe. The Pristine survey, led by the Leibniz Institute for Astrophysics Potsdam (AIP) and the University of Strasbourg, is looking for exactly these pristine stars.

    To find these oldest messengers among the overwhelming population of younger stars is no easy task. Just after the Big Bang, the Universe was filled with hydrogen and helium and a bit of lithium. No heavier elements were around, as these are only synthesized in the hot interior of stars – and those did not exist yet. Our Sun has about 2 % of heavier elements in its atmosphere, as can be seen when we make a spectrum of its light. Because of this fact, astrophysicists can conclude that the sun has emerged as part of a later generation of stars – and has “recycled” in its atmosphere the products of the stars that lived long before it and have since died out. In searching for the oldest stars, scientists look for stars with much more pristine atmospheres than our Sun. The more pristine the atmosphere, the earlier the generation in which this star was born. Studying stars of different generations allows us to understand the formation history of the Galaxy – an area of research that therefore is also called near-field cosmology.

    Chemical abundance

    The Pristine team used a special narrow band filter on the Canada-France-Hawaii Telescope to preselect candidate stars with pristine atmospheres.


    CFHT Telescope, Maunakea, Hawaii, USA, at Maunakea, Hawaii, USA,4,207 m (13,802 ft) above sea level

    This step was then followed by a detailed spectroscopic campaign with the telescopes of the Isaac Newton Group in Spain and the European Southern Observatory in Chile.

    Isaac Newton Group telescopes, at Roque de los Muchachos Observatory on La Palma in the Canary Islands, Spain, at an altitude of 2400m

    (IAC telescopes identified below.)

    ESO VLT at Cerro Paranal in the Atacama Desert, •ANTU (UT1; The Sun ),
    •KUEYEN (UT2; The Moon ),
    •MELIPAL (UT3; The Southern Cross ), and
    •YEPUN (UT4; Venus – as evening star).
    elevation 2,635 m (8,645 ft) from above Credit J.L. Dauvergne & G. Hüdepohl atacama photo

    EPFL’s researchers Pascale Jablonka and Carmela Lardo formed one out of three teams, with the Paris Observatory and the Instituto de Astrofísica de Canarias, in charge of the spectroscopic analysis and the chemical abundance measurements, that led to the identification of this very special star. They could demonstrate that the star had indeed very few heavy elements in its atmosphere.

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    “Pristine 221 spectrum shows a lot of hydrogen lines and very few other elements except a small amount of calcium. This tells us that the star is ultra metal-poor. This unusual lack of heavier elements in its atmosphere means that it probably belongs to an early generation of stars formed in the Galaxy.”

    Most elements are depleted by factors 10.000 to 100.000 compared to the Sun. Additionally, its detailed pattern of different elements stands out. Whereas usually extremely metal-poor stars show a very large enhancement in carbon, this star does not. This makes this star the second of its kind and an important messenger from the early Universe“, says Else Starkenburg, researcher at AIP and first author of the study.

    “Scientists used to think that carbon was a necessary cooling agent, enabling small fragmentation of the gas cloud from which stars form, and leading to the subsequent formation of low-mass stars in the high-redshift universe, Pascale Jablonka explains. With now two examples of such old and carbon-poor stars, models need to be revised.”

    From IAC article:

    3
    Artistic image of the first supernovas in the Milky Way. Pristine 221.8781 + 9.7844 star formed from the material ejected by these first supernovae. Credit: Gabriel Pérez, SMM (IAC).

    An international team of researchers, with doctors at the Institute of Astrophysics of the Canary Islands David Aguado, Jonay González and Carlos Allende part, has discovered the existence of a very metal-poor star, one of the oldest in the Milky Way and, therefore, an excellent messenger of the early universe.

    Star Pristine 221.8781 + 9.7844 is one of the oldest in the Milky Way. This is known by the chemical composition of the atmosphere. Just after the Big Bang, the universe was filled with hydrogen, helium and some lithium. If there were no heavier elements because they are synthesized inside stars. In the words of researcher David Aguado, “because the atmosphere of the analyzed star is very poor in metals, we can say that is one of the oldest objects in the Milky Way and, of course, before the birth of the sun.” And he adds: “This star is going to help us better understand certain aspects of the origin of the Milky Way and how the first stars were formed.”

    To reach these conclusions, have made detailed follow-up studies with ISIS instrument, the William Herschel Telescope, and the IDS instrument on the telescope Isaac Newton, both of the Isaac Newton Group of Telescopes (ING), installed in the Roque de los Muchachos Observatory (Garafía, La Palma). “The spectroscopic images of intermediate resolution, obtained in INT and WHT telescopes on La Palma have enabled us to check the low carbon content, which in this type of stars is usually very abundant,” says Carlos Allende, one of the researchers this project.


    ING 4 meter William Herschel Telescope at Roque de los Muchachos Observatory on La Palma in the Canary Islands, 2,396 m (7,861 ft)


    NG Isaac Newton 2.5m telescope at Roque de los Muchachos Observatory on La Palma in the Canary Islands, Spain, Altitude 2,344 m (7,690 ft)

    This study also used high-resolution spectroscopy obtained with the UVES spectrograph on the VLT (Paranal, ESO).

    UVES spectrograph mounted on the VLT at the Nasmyth B focus of UT2

    “The spectroscopic data of high resolution UVES on the VLT have led to measure the abundance of lithium in the atmosphere of this star, which provides additional information about the origin of the Universe,” says Jonay González, researcher Ramon y Cajal IAC and collaborator Pristine in the project.

    Team on the paper:

    Else Starkenburg David S. Aguado, Piercarlo Bonifacio, Elisabetta Caffau, Pascale Jablonka, Carmela Lardo, Nicolas Martin, Ruben Sanchez-Janssen, Federico Sestito, Kim A.Venn, Kris Youakim, Carlos Allende Prieto, Anke Arentsen, Marc Gentile, Jonay I. Gonzalez Hernandez, Collin Kielty, Helmer H. Koppelman, Nicolas Longeard, Eline Tolstoy, Raymond G. Carlberg, Patrick Côté, Morgan Fouesneau, Vanessa Hill, Alan W. McConnachie, Julio F. Navarro.

    See the full EPFL article here .
    See the full IAC article here.

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    Please help promote STEM in your local schools.

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    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 4:09 pm on October 4, 2018 Permalink | Reply
    Tags: EPFL-École Polytechnique Fédérale de Lausanne, Microscopy technology, , Super-resolution microscopy builds multicolor 3D from 2D, The researchers tested the method on human centriole complexes   

    From École Polytechnique Fédérale de Lausanne: “Super-resolution microscopy builds multicolor 3D from 2D” 

    EPFL bloc

    From École Polytechnique Fédérale de Lausanne

    04.10.18
    Nik Papageorgiou

    1
    Human centrioles labelled with antibodies against two proteins (Cep152, HsSAS-6) and imaged using super-resolution microscopy. From many individual particles showing projections of the centriole complex in various orientations (upper panel), by using a fused intermediate (yellow, lower panel), the newly developed method allows now to reconstruct a multicolor 3D model (lower panel) (credit: Christian Sieben/EPFL).

    A new technique developed by EPFL overcomes the noise and color limitations of super-resolution microscopy by creating three-dimensional reconstructions from single-color, two-dimensional images of protein complexes.

    Super-resolution microscopy is a technique that can “see” beyond the diffraction limit of light. The technique has garnered increasing interest recently, especially since its developers won the Nobel Prize in Chemistry in 2014. By exploiting fluorescence, super-resolution microscopy now allows scientists to observe cells and their interior structures and organelles in a way never before possible.

    Many of the molecular complexes inside cells are made up of multiple proteins. Since current techniques of super-resolution microscopy typically can only use one or two fluorescent colors, it is difficult to observe different proteins and decipher the complex architecture and underlying assembly mechanisms of the cell’s interior structures. An even greater challenge is to overcome the noise inherent to the super-resolution methods and fluorescent labeling, to achieve the full resolution potential.

    Scientists from the lab of Suliana Manley at EPFL have now solved both problems by developing a new method to analyze and reconstruct super-resolution images and re-align them in a way that multiple proteins can be placed within a single 3D volume. The method works with images taken with large field-of-view super-resolution microscopy, with each image containing hundreds of two-dimensional projections of a labeled structure in parallel.

    Each 2D view represents a slightly different orientation of the structure, so that with a dataset of thousands of views, the method can computationally reconstruct and align the 2D images into a 3D volume. By combining information from a large number of single images, the noise is reduced and the effective resolution of the 3D reconstruction is enhanced.

    With the help of Pierre Gönczy’s lab at EPFL, the researchers tested the method on human centriole complexes. Centrioles are pairs of cylindrical molecular assemblies that are crucial in helping the cell divide. Using the new multicolor super-resolution reconstruction method, the researchers were able to uncover the 3D architecture of four proteins critical for centriolar assembly during organelle biogenesis.

    The new approach allows for unlimited multiplexing capabilities. “With this method, if the proteins in the structure can be labeled, there is no limit to the number of colors in the 3D reconstruction,” says Suliana Manley. “Plus, the reconstruction is independent of the super-resolution method used, so we expect this analysis method and software to be of broad interest.”

    Funding
    European Research Council (ERC)
    EPFL
    Horizon 2020 (MSCA-COFUND)
    NCCR Chemical Biology

    Science paper:
    Multicolor single-particle reconstruction of protein complexes
    Nature Methods

    See the full article here .

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    Please help promote STEM in your local schools.

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    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 2:57 pm on October 1, 2018 Permalink | Reply
    Tags: EPFL-École Polytechnique Fédérale de Lausanne, , Microresonators offer a simpler approach to sensing with light pulses, Spatial multiplexing   

    From École Polytechnique Fédérale de Lausanne: “Microresonators offer a simpler approach to sensing with light pulses” 

    EPFL bloc

    From École Polytechnique Fédérale de Lausanne

    01.10.18
    Erwan Lucas
    Nik Papageorgiou

    1
    Artist’s rendering of multiplexed optical pulses in a crystalline resonator (credit: Woogieworks)

    Researchers at EPFL have found a way to implement an optical sensing system by using spatial multiplexing, a technique originally developed in optical-fiber communication. The method, which produces three independent streams of ultrashort optical pulses using a single continuous-wave laser and a single optical microresonator, is far simpler than existing technologies.

    Ultrashort optical pulses are becoming more and more relevant in a number of applications including distance measurement, molecular fingerprinting and ultrafast sampling. Many of these applications rely not only on a single stream of pulses – also known as “optical frequency combs” – but require two or even three of them. Nonetheless, these multi-comb approaches significantly speed up acquisition time over conventional techniques.

    These trains of short optical pulses are typically produced by large pulsed laser sources. Multi-comb applications therefore require several such lasers, often at prohibitive costs and complexity. Furthermore, the relative timing of pulse trains and their phases must be very well synchronized, which requires active electronics that synchronize the lasers.

    In a new paper published in Nature Photonics, the research team of Tobias J. Kippenberg at EPFL, together with the group of Michael Gorodetsky at the Russian Quantum Centre, has developed a much simpler method to generate multiple frequency combs. The technology uses small devices called “optical microresonators” to create optical frequency combs instead of conventional pulsed lasers.

    The microresonator consists of a crystalline disk of a few millimeters in diameter. The disk traps a continuous laser light and converts it into ultrashort pulses – solitons – thanks to the special nonlinear properties of the device. The solitons travel around the microresonator 12 billion times per second. At every round, a part of the soliton exits the resonator, producing a stream of optical pulses.

    The microresonator the researchers used here has a special property in that it allows the light to travel in the disk in multiple different ways, called spatial modes of the resonator. By launching continuous lightwaves in several modes at the same time, multiple different soliton states can be obtained simultaneously. In this way, the scientists were able to generate up to three frequency combs at the same time.

    The working principle is the same as spatial multiplexing used in optical fiber communication: the information can be sent in parallel on different spatial modes of a multimode fiber. Here, the combs are generated in distinct spatial modes of the microresonator.

    The method has several advantages, but the primary one is that it does not require complex synchronization electronics. “All the pulses are circulating in the same physical object, which reduces potential timing drift, as encountered with two independent pulsed lasers,” explains Erwan Lucas, first author of the paper. “We also derive all the continuous waves from the same initial laser by using a modulator, which removes the need for phase synchronization.”

    2
    An illustration of the concept behind the new method (credit: Erwan Lucas/EPFL)

    Using this multiplexing scheme, the team demonstrated several applications, such as dual-comb spectroscopy, or rapid optical sampling. The acquisition time could be adjusted between a fraction of a millisecond to 100 nanoseconds.

    The authors are now working on developing a new demonstration with the triple-comb source: “We had not planned for a demonstration, as we did not expect our scheme to work so easily,” says Lucas. “We are obviously working on it.”

    The technology can be integrated with both photonic elements and silicon microchips. Establishing multi-comb generation on a chip may catalyze a wide variety of applications such as integrated spectrometers or LIDAR, and could make optical sensing far more accessible.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    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 1:48 pm on April 24, 2018 Permalink | Reply
    Tags: , , , , EPFL-École Polytechnique Fédérale de Lausanne, Studying dwarf galaxies to get the big picture   

    From École Polytechnique Fédérale de Lausanne EPFL: “Studying dwarf galaxies to get the big picture” 

    EPFL bloc

    École Polytechnique Fédérale de Lausanne EPFL

    23.04.18
    Sarah Perrin

    1
    Calalog of the studied dwarf galaxies’ haloes. © 2018 EPFL/LASTRO

    EPFL scientists have completed the fastidious task of analyzing 27 dwarf galaxies in detail, identifying the conditions under which they were formed and how they’ve since evolved. These small-scale galaxies are perfect for studying the mechanisms of new star formation and the very first steps in the creation of the universe.

    Dwarf galaxies don’t emit much light and are therefore hard to observe, but they have a lot to teach us about how the universe was created. A team of scientists from EPFL’s Laboratory of Astrophysics (LASTRO) meticulously studied 27 such galaxies and found a surprising degree of variation in the mechanisms by which their stars were formed. The results of their painstaking work was published in Astronomy & Astrophysics.

    “Dwarf galaxies are the smallest and probably the oldest galaxies in the universe. Under standard cosmology theory, larger galaxies are formed by the merger of these smaller ones,” says Yves Revaz, a galaxy dynamics expert at LASTRO.

    While they may be called “dwarves,” they are in fact huge and can weigh anywhere between hundreds of thousands and several million times as much as the sun. They are also the galaxies with the most dark matter. The LASTRO team therefore had to develop highly sophisticated computer models to study these galaxies’ properties, size and temporality – all of which go well beyond our basic understanding.

    Their models take into account each of the galaxies’ components – gases, stars and dark matter – as well as the relationship between dark matter and visible matter (called “baryonic matter” in astrophysics). The models also factor in the conditions under which matter was formed when the universe was first created some 14 billion years ago – conditions that are now known thanks to recent space missions carried out to discover the signatures of the Big Bang.


    Step by step

    To analyze the dwarf galaxies, the scientists first took each model and went step by step through the galaxies’ key characteristics like how much gas (mainly hydrogen) they contain, the heating and cooling of their interstellar mediums, their compression and expansion processes, the successive generations of their stars, those stars’ supernovae, and the resulting release of an array of chemicals. The scientists then compared the results of their models with data that had been obtained by observing dwarf galaxies – more specifically, those orbiting our galaxy, the Milky Way, and its neighboring galaxy, Andromeda (M31) – using eight-meter optical telescopes, the biggest that are currently out there. These dwarf galaxies form part of what is called the Local Group and are close enough for astrophysicists to be able to obtain accurate information on the ages and chemical components of individual stars.

    Local Group. Andrew Z. Colvin 3 March 2011

    Making sure that the models’ results match empirical data is essential if the scientists want to use them to test their theories about dark matter, the kinds of objects responsible for the reionization of the universe, and the conditions and time periods for new star formation.

    This is the first time that dwarf galaxies have been examined in such detail and under cosmologic conditions – that is, not by considering them as isolated systems but rather by taking into account all the interactions among the very first galactical systems.

    Excellent guinea pigs

    “The advantage of dwarf galaxies is that they respond very well to even minor changes in conditions, making them excellent guinea pigs for studying galaxies in general,” says Pascale Jablonka, a LASTRO researcher specialized in spectroscopy and galaxies’ chemical development and co-author of the study. For instance, by analyzing the light that stars emit, she was able to determine their chemical composition and how long it took them to form.

    “Our models enabled us to create a database of many different types of stellar activity and gave us valuable insight into the factors that can cause star formation to speed up, slow down or even stop altogether,” says Revaz.

    Based on the data they collected – which include an impressive number of different star-formation mechanisms given how “small” dwarf galaxies are – the LASTRO team found that the specific mechanism used depends on the density of the galaxy’s dark and baryonic matter. That density determines whether a galaxy will keep on making stars or suddenly stop. If a dwarf galaxy’s matter is too dispersed, then its hydrogen will get too hot and evaporate, meaning it can no longer form stars. If on the other hand a dwarf galaxy has a dense halo of dark matter protecting it, then star formation will continue apace.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

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    EPFL is Europe’s most cosmopolitan technical university with students, professors and staff from over 120 nations. A dynamic environment, open to Switzerland and the world, EPFL is centered on its three missions: teaching, research and technology transfer. EPFL works together with an extensive network of partners including other universities and institutes of technology, developing and emerging countries, secondary schools and colleges, industry and economy, political circles and the general public, to bring about real impact for society.

     
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