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  • richardmitnick 8:39 am on August 31, 2016 Permalink | Reply
    Tags: 16.2 million Euros for neutron and positron research, , , TUM   

    From TUM: “16.2 million Euros for neutron and positron research” 

    Techniche Universitat Munchen

    Techniche Universitat Munchen

    28.08.2016
    Desk:
    Andrea Voit (FRM2)

    S. Reiffert (TUM)
    reiffert@zv.tum.de

    The German Federal Ministry of Education and Research (BMBF) has given 13.5 million Euros to fund a number of projects at the Heinz Maier-Leibnitz Zentrum (MLZ). The projects are to be realized by ten different universities over the next three years, including seven projects at the Technical University of Munich (TUM). The Ministry has also given 2.7 million Euros to support the integration of instruments in the new Neutron Guide Hall East at the Heinz Maier-Leibnitz research neutron source (FRM II).

    1
    In the future a combination of x-ray and neutron radiation will make it possible for the tomography system ANTARES to generate even better interior images of batteries. (Photo: Bernhard Ludewig)

    The Maier-Leibnitz Zentrum, a partnership between the Technical University of Munich (TUM) and the Helmholtz Centers in Jülich and Geesthacht, gives scientists access to the neutron and positron instruments at the research neutron source of the Heinz Maier-Leibnitz Zentrum (FRM II) in Garching. The BMBF focus program “Condensed Matter Research with Large Scale Facilities” will support a total of 19 research projects at the MLZ until 2019.

    Three scientific instruments will be completed using this funding over the course of the next three years:
    SAPHiR, the high-pressure press of the Bavarian Research Institute of Experimental Geochemistry and Geophysics in Bayreuth (BGI) is capable of reproducing pressures and temperatures typical of the earth’s interior for the investigation of their effects on geological samples. The neutrons will provide highly precise measurements of stone structures and will thus for example enable analysis of stone folding, while at the same time helping to develop new magnetic storage media.

    At the RWTH Aachen University’s high-intensity neutron time of flight diffractometer POWTEX, the funding will go towards the construction of an innovative wide-area neutron detector. RWTH Aachen University and Göttingen University (Georg-August-Universität) received the funding necessary to develop the associated software.

    Highly polarized neutrons will be realized using the funding for the University of Cologne’s cold three-axis spectrometer KOMPASS. This will enable the investigation of weak magnetic orderings and complex magnetic systems in order to achieve higher storage densities in future PCs.

    Faster measurements with BAMBUS – ERWIN supplements RESI in battery tests

    The Technical University of Dresden’s multi-detector system BAMBUS at the three-axis spectrometer PANDA will use the financial support to increase the speed with which the position and extent of unknown excitations can be found. This improves the efficiency of investigations on potential materials for quantum computers and innovative superconductors.

    The Karlsruhe Institute of Technology is in charge of two additional projects with the goal of observing on a completely non-destructive basis the molecular processes that occur when charging and discharging batteries in order to create higher-performance and longer-lasting batteries: Here the single crystal diffractometer RESI will be extended to include the option ERWIN (Energy Research WIth Neutrons) and the instrument NECTAR for radiography and tomography with thermal neutrons.

    With its project involving the hot single crystal diffractometer HEIDI, the RWTH Aachen University intends to enable investigation of samples ten times smaller than usually viable with neutrons – significantly less than one cubic millimeter – and to provide anvil cells for high-pressure experiments.

    Several professors at the TUM are creating new measurement options using neutrons
    The BMBF is also supporting six projects at the TUM Physics department:

    Alloys for new high-performance materials for gas turbines have to withstand very high temperatures of up to 1200°C while retaining tensile strength and staying pressure-resistant. Dr. Ralph Gilles is building a high-temperature oven and a cooling unit to test these alloys with neutrons.

    Prof. Peter Böni and Dr. Robert Georgii are constructing a module that can be used with various different instruments and makes it possible to measure magnetic and structural excitations at small scattering angles even in strong magnetic fields.

    Prof. Christian Pfleiderer is planning an extension for the neutron spin echo spectrometer RESEDA that will increase neutrons intensity in strong magnetic fields with ultra-high resolution.

    In the future a combination of x-ray and neutron radiation will make it possible for the tomography system ANTARES to generate even better interior images of batteries. The project, dubbed NeuRoFast, is coordinated by Prof. Franz Pfeiffer.

    Prof. Bastian Märkisch is further enhancing the instrument PGAA in order to make even higher resolution measurements of deeper layers of lithium in batteries and boron in photovoltaic cells containing silicon.

    As a result of the BMBF funding awarded to Prof. Peter Müller-Buschbaum (TUM), the time of flight spectrometer TOFTOF will receive a new sample environment making it possible for example to observe bacterial proteins during photosynthesis.

    Shorter measurement periods for positrons

    RWTH Aachen University is expanding the biological laboratory to enable able scientists to investigate proteins in addition to neutrons with other spectroscopic instruments at the MLZ. In the future investigation of the three-dimensional ordering of nano-particles will be possible with the software product BornAgain, enhanced by the FAU (Friedrich-Alexander-Universität) Erlangen-Nuremberg.

    In addition to neutron instruments, the world’s most intensive positron source is also being expanded at the FRM II with the BMBF funds.

    Among other things the Bundeswehr University Munich (UniBwM) is expanding the scanning positron microscope and pulsed positron beam to make more measurements with electron anti-particles possible within a shorter period of time.

    Dr. Christoph Hugenschmidt of the Technical University of Munich is developing a completely innovative positron instrument for high-precision determination of surface structures and the three-dimensional distribution of crystal defects.

    “Unprecedented spectrum of life and health sciences”

    Prof. Winfried Petry, scientific director of the FRM II and MLZ, comments: “The joint BMBF research is an ideal way to integrate university research in the utilization of the MLZ. At the same time we can attract the most highly coveted measurement guests in the world with new construction and continuing improvement of scientific instruments.”

    Prof. Brückel, director of the Jülich Centre for Neutron Scattering (JCNS) and scientific director at the MLZ, adds: “In the projects supported, the Heinz Maier-Leibnitz Zentrum covers an unprecedented spectrum of life and health sciences ranging from protein research to nano-sciences and engineering sciences, all the way to energy research for battery systems.”

    The Heinz Maier-Leibnitz Zentrum (MLZ) is a leader in cutting-edge research with neutrons and positrons. As a facility for scientific users at the FRM II research neutron source, the MLZ offers a unique selection of approximately 30 high-performance neutron measuring instruments to visiting scientists. The MLZ is a partnership of the Technical University of Munich (TUM), the Forschungszentrum Jülich and the Helmholtz-Zentrum Geesthacht Center for Materials and Coastal Research (HZG). This partnership is financially supported by the German Federal Ministry of Education and Research (BMBF) and the Bavarian State Ministry for Education and Culture, Science and the Arts. Other universities and the Max-Planck-Gesellschaft are also involved with the measuring instruments of the MLZ.

    The research neutron source Heinz Maier-Leibnitz (FRM II) provides neutron beams for research, industry and medicine. It is operated by the Technical University of Munich (TUM) and financed by the Bavarian State Ministry for Education and Culture Science and the Arts.

    See the full article here .

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    Techniche Universitat Munchin Campus

    Technische Universität München (TUM) is one of Europe’s top universities. It is committed to excellence in research and teaching, interdisciplinary education and the active promotion of promising young scientists. The university also forges strong links with companies and scientific institutions across the world. TUM was one of the first universities in Germany to be named a University of Excellence. Moreover, TUM regularly ranks among the best European universities in international rankings.

     
  • richardmitnick 10:27 am on August 29, 2016 Permalink | Reply
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    From TUM: “Meteorite Impact on a Nano Scale” 

    Techniche Universitat Munchen

    Techniche Universitat Munchen

    2016-08-29
    Prof. Friedrich Aumayr
    Institute of Applied Physics
    TU Wien
    Wiedner Hauptstraße 8-10, 1040 Wien
    T: +43-1-58801-13430
    friedrich.aumayr@tuwien.ac.at

    Dipl.-Ing. Elisabeth Gruber
    Institute of Applied Physics
    TU Wien
    Wiedner Hauptstraße 8-10, 1040 Wien
    T: +43-1-58801-13435
    elisabeth.gruber@tuwien.ac.at

    1
    Elisabeth Gruber in the lab at TU Wien

    2
    Nanostructures on a crystal after ion bombardment: Trenches with nanohillocks on either side are created. At the impact site, a particularly large nanohillock is formed.

    Intricate nanostructures can be created on crystal surfaces by hitting them with high energy ions. Scientists from TU Wien (Vienna) can now explain these remarkable phenomena.

    A meteorite impacting the earth under a grazing angle of incidence can do a lot of damage; it may travel a long way, carving a trench into the ground until it finally penetrates the surface. The impact site may be vaporized, there can be large areas of molten ground. All that remains is a crater, some debris, and an extensive trail of devastation on both sides of the impact site.

    Hitting a surface with high-energy, heavy ions has quite similar effects – only on a much smaller scale. At TU Wien (Vienna), Prof. Friedrich Aumayr and his team have been studying the microscopic structures which are formed when ions are fired at crystals at oblique angles of incidence.

    Trenches and Ridges

    “When we take a look at the crystal surface with an atomic force microscope, we can clearly see the similarities between ion impacts and meteorite impacts”, says Elisabeth Gruber, PhD-student in Friedrich Aumayrs team. “At first the projectile, scratching across the surface at a grazing angle, digs a trench into the crystal surface, which can be hundreds of nanometers long. Extensive ridges appear on either side of the trench, consisting of tiny structures called nanohillocks.” When the projectile ultimately enters the crystal and disappears, an especially large hillock is created at the impact site. Beyond that, the ion keeps moving below the surface, until it finally comes to a halt.

    This may sound simple and obvious, as if high energy ions just behaved like tiny, electrically charged bullets. But in fact, it is not at all self-evident that objects on a nano scale behave like macroscopic objects do. When atoms exchange energy, quantum physics always plays an important role.

    “When the high-energy ions interact with crystal surfaces – calcium fluoride, in our case – many different physical effects have to be taken into account”, says Friedrich Aumayr. “Electrons can change their energy state, they can exchange energy with atoms around them and excite vibrations in the crystal lattice, the so-called phonons. We have to carefully consider all these effects when we want to understand how the nanostructures on the crystal surface are created.”

    Melting and Evaporation

    In order to understand the mechanism leading to the nano-trenches and hillocks, the team developed extensive computer simulations, together with colleagues from Germany. “That way we can determine, how much different parts of the crystal surface are heated up”, says Elisabeth Gruber. “There are regions which become so hot that the material melts, at certain points it can even evaporate. When we know how large these regions are, we can predict very accurately what the nanostructures on the crystal surface will look like.”

    The goal of this line of research is not only to understand how tailored nanostructures can be created. It is also important to find out how different materials are harmed by heavy ion bombardment. “Calcium fluoride is often used as an insulator in semiconductor technology”, says Friedrich Aumayr. “We want our electronics to work, even under extreme conditions, for instance in a satellite which is exposed to cosmic radiation.” When the calcium fluoride layer is riddled with tiny holes, it can cause the device to short circuit and fail. Therefore, it is vital to understand the interaction of crystal surfaces and fast ions.

    Original publication:
    E. Gruber et al., Swift heavy ion irradiation of CaF2 – from grooves to hillocks in a single ion track 405001 Journal of Physics: Condensed Matter 28 (2016)

    See the full article here .

    Please help promote STEM in your local schools.

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    Techniche Universitat Munchin Campus

    Technische Universität München (TUM) is one of Europe’s top universities. It is committed to excellence in research and teaching, interdisciplinary education and the active promotion of promising young scientists. The university also forges strong links with companies and scientific institutions across the world. TUM was one of the first universities in Germany to be named a University of Excellence. Moreover, TUM regularly ranks among the best European universities in international rankings.

     
  • richardmitnick 9:58 am on August 29, 2016 Permalink | Reply
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    From TUM: “A look at the molecular quality assurance within cells” 

    Techniche Universitat Munchen

    Techniche Universitat Munchen

    25.08.2016
    Technical University of Munich
    Prof. Dr. Matthias J. Feige
    matthias.feige@tum.de
    +49-89-28910595
    http://www.cell.ch.tum.de

    1
    A look at the molecular quality assurance within cells. (Illustration: Joshua Stokes, St. Jude Children’s Research Hospital)

    Proteins fulfill vital functions in our body. They transport substances, combat pathogens, and function as catalysts. In order for these processes to function reliably, proteins must adopt a defined three-dimensional structure. Molecular “folding assistants”, called chaperones, aid and scrutinize these structuring processes. With participation from the Technical University of Munich (TUM), a team of researchers has now revealed how chaperones identify particularly harmful errors in this structuring process. The findings were published in the scientific journal “Molecular Cell”.

    Chaperones are a kind of Technical Inspection Authority for cells. They are proteins that inspect other proteins for quality defects before they are allowed to leave the cell.

    If a car does not pass its technical inspection, it implies that it has severe defects that could lead to serious accidents. If a protein folds into a faulty structure, this may lead to serious diseases. Examples of these are neurodegenerative disorders such as Alzheimer’s, but also metabolic diseases such as cystic fibrosis and diabetes.

    Matthias Feige, professor for cellular protein biochemistry at the TUM, worked within a team headed by Linda Hendershot at St. Jude Children’s Research Hospital in Memphis/TN, USA, to investigate how chaperones identify structurally flawed proteins. In the study, the scientists focused on proteins which are produced in a part of the cell called the endoplasmic reticulum. “We are mainly interested in cellular protein folding”, explains Feige. “How the self-organization of proteins occurs at the molecular level – and how cells identify errors in this process – is a truly fascinating question.”

    Defective proteins need to be eliminated by the cell

    The endoplasmic reticulum consists of a network of hollow spaces and tubules. It is specialized in protein folding and the quality control for this process, and a third of all human proteins are produced here. Just like in any production process, errors may occur: Proteins form a folding core mostly made up of hydrophobic (water-repellent) amino acids, around which the rest of the protein is able to structure itself. However, if errors occur in the folding process, these hydrophobic areas may not be buried in the core, but instead be exposed on the surface of a protein where they may result in proteins clumping together. This can become hazardous to the cell or the entire organism.

    Into the cell via a shuttle

    Thus far, scientists knew that chaperones were able to identify general hydrophobic amino acid sequences if they remained exposed on protein surfaces. However, not all proteins which present such sequences should necessarily be degraded. That is because not all proteins with hydrophobic amino acid sequences on the surface are defective. How exactly the cell decides if a protein is so dangerous that it needs to be eliminated remained a mystery.

    The researchers developed a new method which made it possible to observe the behavior of chaperones in the living biological system of the cell. To do this, they inserted precisely defined sequences of amino acids, which are the building blocks of proteins, into a shuttle system that transported them into the endoplasmic reticulum within the cell. Via this ingenious trick, they were able to observe, under biologically relevant conditions, which sequences the various chaperones recognized.

    Two classes of chaperones

    What they discovered was that there existed not only one, but two classes of chaperones in the endoplasmic reticulum, each of which identifies different types of hydrophobic amino acid sequences. Furthermore, the sequences identified by the chaperones of the second class, which are described in this journal article for the first time, form particularly dangerous clumps in the cell. Once they are identified, the proteins possessing them can be eliminated rapidly.

    “This is an important piece in the puzzle of how molecular quality control functions”, says Feige. “Follow-up studies will now be required to see how the chaperones recognize their target sequences on a structural level.”

    This research is also important for the biotechnological production of proteins, such as antibodies. In order to prevent these pharmaceutical products from being broken down by the body too quickly, biotechnologists can now ensure that the corresponding sequences do not appear on the surface of the proteins.

    Publication: Julia Behnke, Melissa J. Mann, Fei-Lin Scruggs, Matthias J. Feige, Linda M. Hendershot, “Members of the Hsp70 Family Recognize Distinct Types of Sequences to Execute ER Quality Control“, Molecular Cell, published online August 18, 2016

    See the full article here .

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    Techniche Universitat Munchin Campus

    Technische Universität München (TUM) is one of Europe’s top universities. It is committed to excellence in research and teaching, interdisciplinary education and the active promotion of promising young scientists. The university also forges strong links with companies and scientific institutions across the world. TUM was one of the first universities in Germany to be named a University of Excellence. Moreover, TUM regularly ranks among the best European universities in international rankings.

     
  • richardmitnick 8:34 am on August 13, 2016 Permalink | Reply
    Tags: , , , TUM   

    From TUM: “Interaction of Earth with supernova remnants lasting for one million years” 

    Techniche Universitat Munchen

    Techniche Universitat Munchen

    10.08.2016
    Contact
    Technical University of Munich
    Prof. Dr. Shawn Bishop
    Tel.: +49 89 289 12437
    shawn.bishop@tum.de

    1
    Starry sky through trees. When massive stars with more than ten solar masses have, at the end of their evolution, consumed all of their nuclear fuel supply, they collapse under their gravity and terminate in so-called core-collapse supernovae. (Photo: kaalimies / fotolia)

    Physicists from the Technical University of Munich (TUM) have succeeded in detecting a time-resolved supernova signal in the Earth’s microfossil record. As the group of Prof. Shawn Bishop could show, the supernova signal was first detectable at a time starting about 2.7 million years ago. According to the researcher’s analyses, our solar system spent one Million years to transit trough the remnants of a supernova.

    When massive stars with more than ten solar masses have, at the end of their evolution, consumed all of their nuclear fuel supply, they collapse under their gravity and terminate in so-called core-collapse supernovae. Thereby they eject huge amounts of matter into their surroundings. If a supernova occurs sufficiently close to our solar system, it should leave traces of supernova debris on Earth, in the form of specific radioisotopes.

    Among the elemental species known to be produced in these stars, the radioisotope Fe-60 stands out: This radioisotope has no natural, terrestrial production mechanisms; thus, a detection of Fe-60 atoms within terrestrial reservoirs is proof for the direct deposition of supernova material within our solar system.

    Increased concentration also found in lunar samples

    An excess of Fe-60 was already observed in around two million year old layers of a ferromanganese (FeMn) crust retrieved from the Pacific Ocean and, most recently, in lunar samples. These Fe-60 signals have been attributed to depositions of supernova ejecta. However, due to the slow growth rate of the FeMn crust, the Fe-60 signal had a poor temporal resolution; while lunar regolith cannot record time information because sedimentation does not occur on the moon.

    Now for the first time, physicists of the group of Shawn Bishop, TUM Professor on Nuclear Astrophysics, succeeded in discovering a time-resolved supernova signal in the Earth’s microfossil record, residing in biogenically produced crystals from two Pacific Ocean sediment drill cores. The onset of the Fe-60 signal occurs at around 2.7 Million years and is centered at around 2.2 Million years. The signal significantly ends around 1.7 Million years.

    “Obviously, the solar system spent on Million years to transit through the debris of a supernova,” says Shawn Bishop, who is also a principal investigator at the Excellence Cluster Universe.

    Samples with excellent stratigraphic resolution

    To analyse the entire temporal structure of the Fe-60 signal in terrestrial samples, a geological reservoir with an excellent stratigraphic resolution and high Fe-60 sequestration and low Fe mobility is required, which preserves the Fe-60 fluxes nearly so as they were at the time of deposition, apart from Fe-60 radioactive decay.

    These conditions are fulfilled in the marine sediments from the Pacific Ocean used in this study. At the time of the Fe-60 deposition, iron-sequestering bacteria that live in the ocean sediments incorporated the Fe-60 within their intracellularly-grown chains of magnetite nanocrystals (Fe3O4). After cell death they have fossilized into microfossils. These sediments have grown with a constant sedimentation rate, preserving the intrinsic temporal shape of the supernova signal. “Nevertheless, the Fe-60 concentration in these fossils is so low that it is detectable only by means of ultrasensitive accelerator mass spectroscopy (AMS)”, says Dr. Peter Ludwig, researcher in the group of Shawn Bishop. At the tandem accelerator at the Maier-Leibnitz Laboratory in Garching the physicists could refine the sensitivity of the method so that this discovery was possible the first time ever.

    Supernova event at a distance of at least 300 light years

    The most plausible progenitor star that gave rise to this supernova likely originated in the Scorpius-Centaurus OB association, as analyses of its relative motion have shown. Around 2.3 million years ago it was located at a minimum distance of about 300 light years to the solar system. Over the course of the last 10 to 15 million years, a succession of 15 to 20 supernovae has occurred in this star association. This series of massive stellar explosions has produced a largely matter-free cavity in the interstellar medium of a galactic arm of the Milky Way. Astronomers call this cavity, in which our solar system is located, the Local Bubble.

    Acknowledgement

    In addition to the TUM’s physicists there were also involved: Researchers from the Central Institute for Meteorology and Geodynamics, Geomagnetism and Gravimetry, Vienna, from the TUM Chemistry Department, Elektronenmikroskopie, as well as from the Helmholtz-Zentrum Dresden-Rossendorf, Helmholtz Institute Freiberg for Resource Technology, Dresden.

    The research was funded by the German Research Foundation (DFG) and the Excellence Cluster Universe

    Original publication

    Ludwig et al.: Time resolved 2-million-year-old supernova activity discovered in Earth’s microfossil record
    Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1601040113, August 8, 2016

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

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    Techniche Universitat Munchin Campus

    Technische Universität München (TUM) is one of Europe’s top universities. It is committed to excellence in research and teaching, interdisciplinary education and the active promotion of promising young scientists. The university also forges strong links with companies and scientific institutions across the world. TUM was one of the first universities in Germany to be named a University of Excellence. Moreover, TUM regularly ranks among the best European universities in international rankings.

     
  • richardmitnick 7:20 am on July 15, 2016 Permalink | Reply
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    From TUM- Leukemia:”The key to self-destruction” 

    Techniche Universitat Munchen

    Techniche Universitat Munchen

    14.07.2016
    PD Dr. Philipp J. Jost
    III. Medizinische Klinik und Poliklinik
    Klinikum rechts der Isar
    Technical University of Munich
    Tel: +49 (89) 4140-5941
    philipp.jost@tum.de

    1
    In Cancer Cell Ulrike Höckendorf and Dr. Philipp Jost describe a new molecular signaling pathway for self-destruction that is suppressed in leukemia cells. (Foto: Heddergott / TUM)

    When adults develop blood cancer, they are frequently diagnosed with what is referred to as acute myeloid leukemia. The disease is triggered by pathological alterations of bone marrow cells, in which, in addition, an important mechanism is out of action: these cells do not die when they are damaged. Researchers from the Technical University of Munich (TUM) have now discovered a molecular signaling pathway for self-destruction that is suppressed in leukemia cells.

    Leukemia involves pathological alterations in the body’s hematopoietic system. In acute myeloid leukemia, it is specifically the bone marrow (Greek: myelos) that is affected. In a healthy body, different blood cells, which perform different functions in the blood, are formed from stem cells and what is referred to as progenitor cells in the bone marrow. A genetic mutation can lead to alterations in stem cells and progenitor cells and turn them into leukemia-initiating cells, which are referred to as LICs for short. Like healthy progenitor cells, LICs multiply in the bone marrow. The genetic mutation, however, causes LICs to remain without function and prevents them from developing into mature blood cells, which ultimately leads to the repression of healthy hematopoiesis in the bone marrow and the onset of leukemia symptoms.

    The most frequent genetic alterations in myeloid leukemia include mutations in the FLT3 gene. A team led by Dr. Philipp Jost from the Department of Hematology/Oncology at Klinikum rechts der Isar at the Technical University of Munich has now discovered that the effects of this gene on pathologically altered cells in a way provide certain indications for the treatment of the disease. The mutation causes a permanent activation of the FLT3 gene. As demonstrated by the scientists, this triggers inflammation-like stimuli in the cell, subjecting it to permanent stress.

    Growth despite inflammation and damage

    Under normal circumstances, such permanent inflammatory stimuli would trigger a program known as programmed cell death to replace damaged cells. This is a kind of self-destruction mechanism used by a cell to initiate its own destruction in a coordinated fashion and allow it to be replaced by a healthy one. “By contrast, LICs manage to grow and proliferate despite the inflammation and damage,” states Philipp Jost. “In our study, we have taken a closer look at the molecular causes of this resistance.”

    To gain a better understanding of the research project described by the TUM scientists in the medical journal Cancer Cell, it is important to understand that cells have different ways of self-destructing. So far, the primary research focus in trying to ascertain why cancer cells survive longer than they should has been placed on a process called apoptosis. However, the fact that inflammatory processes occur in LICs pointed Philipp Jost and his colleagues in a different direction. Another way to initiate cell death is through what is referred to as necroptosis. Whereas, in apoptosis, a cell shrinks in a coordinated fashion, in necroptosis, a sudden destruction occurs, which releases the contents of the dying cell along with numerous messenger substances. This induces a strong inflammatory stimulus in the vicinity of the cell.

    Cancer cells block activation of protein

    Necroptosis is triggered by the activation of a protein called RIPK3, which subsequently initiates processes within the cell that lead to its death. The scientists used cell cultures to discover that leukemia takes a particularly severe course when RIPK3 is blocked inside LICs. This led to the cancer cells surviving particularly long, accompanied by their strong division and conversion to functionless blood cells (blasts). “We conclude from our findings that particularly aggressive cancer cells have the capacity to block RIPK3,” states Ulrike Höckendorf, lead author of the study. “Exactly how they accomplish this, however, remains to be investigated.”
    Inducing cell death in a LIC by means of necroptosis has repercussions which also affect neighboring leukemia cells. The inflammatory stimuli triggered by the substances released during necroptosis are significantly stronger than the processes caused by the mutation in the FLT3 gene in a LIC. This inflammation has positive effects on the area surrounding the cell: induced by the messenger substances, neighboring leukemia cells begin to mature similar to healthy cells, leading to a less aggressive progression of leukemia.

    With cell death blocked – apoptosis, too, is “neutralized” in many cancer cells – individual LICs manage to survive and proliferate even after chemotherapy or radiotherapy. “The new findings on the impact of the RIPK3 signaling pathway and the messenger substances released could open up new options for the treatment of leukemia,” states Philipp Jost. “If it were possible to artificially reproduce the effect of RIPK3 using medication, one could launch a targeted attack on leukemia cells.”

    Original Publication

    U. Höckendorf, Mo. Yabal, T. Herold, E. Munkhbaatar, S. Rott, S. Jilg, J. Kauschinger, G. Magnani, F. Reisinger, M. Heuser, H. Kreipe, K.Sotlar, T. Engleitner, R. Rad, W. Weichert, C. Peschel, J. Ruland, M. Heikenwalder, K. Spiekermann, J. Slotta-Huspenina, O. Groß, P. Jost. RIPK3 Restricts Myeloid Leukemogenesis by Promoting Cell Death and Differentiation of Leukemia Initiating Cells. Cancer Cell Vol. 30:1 (2016). DOI: 10.1016/j.ccell.2016.06.002

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

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    Techniche Universitat Munchin Campus

    Technische Universität München (TUM) is one of Europe’s top universities. It is committed to excellence in research and teaching, interdisciplinary education and the active promotion of promising young scientists. The university also forges strong links with companies and scientific institutions across the world. TUM was one of the first universities in Germany to be named a University of Excellence. Moreover, TUM regularly ranks among the best European universities in international rankings.

     
  • richardmitnick 9:30 am on July 13, 2016 Permalink | Reply
    Tags: , , Prostate cancer treatment, TUM   

    From TUM: “Gamma probe guides surgeons” 

    Techniche Universitat Munchen

    Techniche Universitat Munchen

    13.07.2016
    PD Dr. med. Tobias Maurer
    Klinik und Poliklinik für Urologie
    E-mail: tobias.maurer@tum.de
    Tel.: +49-89-4140-2522

    1
    Radioligands developed at TUM make it possible to visualize metastases while they are still very small. This PET/CT scan shows a metastatic lymph node (arrow). (photo: Nuklearmedizin / TUM)

    Prostate cancer is one of the most common cancers diagnosed in men. Even after surgical removal of the prostate gland, there is still a possibility of new metastases forming in lymph nodes in the pelvis. Researchers from the School of Medicine and the Department of Chemistry at the Technical University of Munich (TUM) have teamed up to develop a method to visualize and remove these metastases while they are still very small.

    Lymph nodes hosting prostate cancer metastases look quite innocuous initially. Since they measure no more than a few millimeters, they cannot be distinguished from their healthy neighbors with the naked eye. On top of this, metastases can also occur in lymph nodes located in parts of the body where doctors would not usually go looking for them. Even the standard imaging methods of magnetic resonance imaging (MRI) and computed tomography (CT) are not able to reliably identify these small metastatic lymph nodes.

    An interdisciplinary team of researchers at TUM have now solved this problem by finding an effective way to make the cancer cells conspicuous. The key to the researchers’ solution is the PSMA (prostate-specific membrane antigen) protein. This protein occurs on the surface of cancer cells in prostate tumors and their metastases, but is otherwise rarely found in the human body.

    Molecule binds specifically to metastases

    The TUM researchers are developing different types of radiolabeled molecules, known as radioligands. Within the body, these bind specifically to proteins – in this case to PSMA, which are found on the cell surface of diseased tissue. If these labeled PSMA-binding molecules are injected into a patient’s bloodstream, they will bind to any metastases they find and emit radiation from there for a limited period. “Since we are working on a molecular scale, the patient will be exposed to just a very low level of radiation. Furthermore, the elements used have a short half-life and can only be detected in the body for anything between a few hours and a few days,” explains Prof. Hans-Jürgen Wester, Chair of Pharmaceutical Radiochemistry.

    By using positron emission tomography (PET) combined with either CT or MRI the now radioactive metastases become visible and can be precisely located. TUM radiochemists, nuclear medicine scientists and urologists are working in close collaboration to develop and apply this method. Physicians will be able to infer from the data whether a surgical intervention would be expedient. They will then make the relevant decision in consultation with the patient, factoring in the results of the PET/CT scan but also considerations such as the patient’s physical state.

    Gamma probe as target tracker

    The ability to radiolabel metastases also opens up new possibilities for the removal of metastatic tissue. Physicians and researchers at TUM and the Klinikum rechts der Isar hospital have jointly developed an operative procedure called PSMA radio-guided surgery to this end. The day before the procedure, the patient receives an infusion with the PSMA radioligand. During the operation, the surgeon examines the tissue using a gamma-ray probe. Working in a similar way to a Geiger counter, the probe measures the radiation and gives the surgical team acoustic and visual feedback.

    “This method allows us to specifically identify metastatic lymph nodes and safely remove them,” explains senior physician Dr. Tobias Maurer from the Department of Urology. With conventional procedures, there is a real possibility that the altered lymph nodes would never be discovered. “With this method, we have had some success in identifying and subsequently removing tumorous lymph nodes that were so small that they had not even been picked up beforehand by our PET/MRI scan,” adds Prof. Markus Schwaiger, Inhaber des Chair of Nuclear Medicine.

    Promising results

    Klinikum rechts der Isar has become a pioneer in the use of PSMA radio-guided surgery. Introduced in 2014, improvements are being made to the procedure all the time. To date, around 60 patients have been treated, with very promising results. Systematic follow-up examinations in a group of 21 patients have shown a reduction of over 90 percent in the biomarker for prostate cancer in ten of the patients. Twelve patients needed no further treatment during the follow-up period of almost one year.

    “Our method could become established as a new and important line of action in the multidisciplinary approach to prostate cancer,” maintains Prof. Jürgen Gschwend, Director of the Department of Urology. If the prostate cancer comes back, even tiny metastases could be removed in suitable patients, who would thus in some cases be able to avoid subsequent hormone or radiation therapy. The procedure will have to be evaluated in the coming months and years. According to Gschwend, identifying the most suitable patients for this treatment will be one of the top priorities.

    Publications

    T. Maurer, K. Schwamborn, M. Schottelius, H-J Wester, M. Schwaiger, J. Gschwend, M. Eiber. PSMA THeranostics Using PET and Subsequent Radioguided Surgery in Recurrent Prostate Cancer. Journal of Clinical Genitourinary Cancer May 2016. DOI: 10.1016/j.clgc.2016.05.020

    T. Maurer, G. Weirich, M. Schottelius, M. Weineisen, B. Frisch, A. Okur, H. Kübler, M. Thalgott, N. Navab, M. Schwaiger, H.-J. Wester, J. Gschwend, M. Eiber. Prostate-specific Membrane Antigen–radioguided Surgery for Metastatic Lymph Nodes in Prostate Cancer. European Urology 68 (2015). DOI: 10.1016/j.eururo.2015.04.034

    M. Eiber, T. Maurer, M. Souvatzoglou, A. Beer, A. Ruffani, B. Haller, F.-P. Graner, H. Kübler, U. Haberhorn, M. Eisenhut, H.-J. Wester, J. Gschwend, M. Schwaiger. Evaluation of Hybrid 68Ga-PSMA Ligand PET/CT in 248 Patients with Biochemical Recurrence After Radical Prostatectomy. Journal of Nuclear Medicine. May 2015. DOI: 10.2967/jnumed.115.154153

    See the full article here .

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    Technische Universität München (TUM) is one of Europe’s top universities. It is committed to excellence in research and teaching, interdisciplinary education and the active promotion of promising young scientists. The university also forges strong links with companies and scientific institutions across the world. TUM was one of the first universities in Germany to be named a University of Excellence. Moreover, TUM regularly ranks among the best European universities in international rankings.

     
  • richardmitnick 9:16 am on May 9, 2016 Permalink | Reply
    Tags: , , TUM, TUM opens central institute for catalysis research   

    From TUM: “TUM opens central institute for catalysis research” 

    Techniche Universitat Munchen

    Techniche Universitat Munchen

    09.05.2016
    Dr. Andreas Battenberg

    1
    The TUM Catalysis Research Center seen from the east – Photo: Andreas Heddergott / TUM

    New research facility inaugurated in Garching

    With the inauguration of the TUM Catalysis Research Center (CRC), the Technical University of Munich (TUM) sets an international highlight in the field of catalysis research. Scientists from five departments, as well as industrial cooperation partners, will collaborate on research under one roof to meet the challenges of energy and resource saving production of chemical raw materials, fine chemicals and pharmaceutical products. Due to the supra-regional significance of the center, the German Federal Ministry of Education and Research (BMBF) contributed to the total construction cost of 84.5 million euro for the newly erected facility.

    Catalysts are the key to sustainable, energy and resource conserving chemical conversion of materials. The use of biogenic raw materials in the future, as well as the extraction, storage and conversion of energy depends on advances in applied catalyst research. The global market for catalysts has topped 18 billion euros and continues to grow. Yet, even fundamental problems like the catalytic utilization of natural gas (methane) to produce refined intermediary chemical products remain unsolved.

    In its new research facility, the TU Munich will tackle the interdisciplinary challenges of modern catalysis as a systems science, bundling available competency from the Departments of Chemistry and Physics and augmenting them with approaches from engineering, computer science and mathematics.

    “In this kind of research, there are no longer borders between the classical disciplines of engineering and natural sciences. Under the shared roof of the Catalysis Research Center we bring widely divergent methodological approaches to convergence,” says TUM President Prof. Wolfgang A. Hermann, who, himself a catalysis researcher, initiated the new research facility. “The product diversity of our technological society will be feasible in the future only if valuable products are produced, excess products decomposed and harmful products avoided through the use of specific catalysts.”

    One of a kind research infrastructure

    The Catalyst Research Center is tightly linked methodically and thematically with existing campus facilities like the Departments of Chemistry, Physics, Mechanical Engineering, Mathematics, and Computer Science, as well as the research center for white biotechnology and the TUM International Graduate School of Science and Engineering (IGSSE), a result of the Excellence Initiative 2006. This is flanked by the newly founded research center for synthetic biotechnology (supported by the Werner Siemens-Stiftung) and various infrastructure facilities, in particular the research neutron source of the Bavarian NMR Center and the supercomputers of the Leibniz Computing Center.

    The center is also home to the strategic research alliance “Munich Catalysis” (MuniCat). In the vein of the “Industry on Campus” concept, TUM scientists work here in collaboration with researchers of Clariant AG to answer important questions in basic and applied research in the field of chemical catalysis. The Wacker Institute of Silicon Technology is a further topically integrated partner in the research program.

    New professorships

    TUM used the planning and construction phases to establish new catalysis-relevant professorships. It extended the spectrum with professorships of bio-organic chemistry, computer-aided biocatalysis, industrial biocatalysis, technical electrochemistry, physical chemistry/catalysis, silicon chemistry, solid body NMR spectroscopy, biomolecular NMR spectroscopy, selective separation technology and systems biology.

    Associated with the CRC are research activities of the Competence Center for Renewable Raw Materials in Straubing where, among other things, ethanol is produced biocatalytically from agricultural products. “The completed expansion of the biochemical and biophysical research facilities at TUM – also with multiple new professorships – strengthens the catalysis focus in the biopharmaceutical domain,” said TUM President Wolfgang A. Hermann. Shortly a new building dedicated to protein research will be erected next to the Catalysis Research Center. “Thus, TUM is now positioned as an international leader with a coherent overall concept.”

    Research center with supraregional significance

    “Hardly any product of the chemical industry would be economically and ecologically feasible without catalysts. Catalysis research is thus a key technology – especially in a raw material poor country like Germany,” said Stefan Müller, parliamentary state secretary in the German Federal Ministry of Education and Research (BMBF). “The TU München is already doing world-class catalysis research. The new center will bolster this position significantly. The construction, which was supported with funding of almost 29 million euro from the BMBF, will thus make an important contribution to strengthening the research location Germany.”

    “With the Departments of Chemistry, Physics, Mechanical Engineering and Computer Science, the TUM neutron research source and the super computers of the Leibniz Computing Center, the research campus Garching has a one of a kind infrastructure worldwide,” said the Bavarian Economic Minister Dr. Ludwig Spaenle. “With the new Catalysis Research Center we have now created a site at which the existing synergies can converge and become effective. We are strengthening the international competitiveness of the scientific and economic regions of Bavaria and Germany with the new Catalysis Research Center.”

    Address: Ernst Otto Fischer-Str. 1

    The street address of new building is Ernst Otto Fischer-Str. 1. Fischer (1918 – 2007) pioneered in organometallic chemistry and was awarded the Nobel Prize in Chemistry in 1973. He held the Chair of Inorganic Chemistry at TUM from 1964 to 1984.

    See the full article here .

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    Technische Universität München (TUM) is one of Europe’s top universities. It is committed to excellence in research and teaching, interdisciplinary education and the active promotion of promising young scientists. The university also forges strong links with companies and scientific institutions across the world. TUM was one of the first universities in Germany to be named a University of Excellence. Moreover, TUM regularly ranks among the best European universities in international rankings.

     
  • richardmitnick 1:27 pm on March 22, 2016 Permalink | Reply
    Tags: , , TUM   

    From TUM: “Sensitive quantum particles” 

    Techniche Universitat Munchen

    Techniche Universitat Munchen

    Important quantum physics phenomenon now more readily measurable

    21.03.2016
    Dr. Markus Hey
    Technical University of Munich
    Physics Department, Chair for Condensed Matter and Many-Body Theory (T34)
    James-Franck-Str., 85747 Garching, Germany
    markus.heyl@tum.de

    1
    Measuring multipartite entanglement (Illustration: Harald Ritsch / IQOQI)

    The quantum mechanical entanglement of particles plays an important role in many technical applications. To date, however, the effect has been difficult to measure experimentally. Physicists from the Technical University of Munich (TUM), the University of Innsbruck and the Institute of Photonic Sciences (ICFO) in Barcelona have now developed a new protocol to detect entanglement of many-particle quantum states using established measuring methods.

    In quantum theory, interactions between particles create fascinating correlations known as entanglement. They cannot be explained by any means known to the classical world. Entanglement is a consequence of the probabilistic rules of quantum mechanics and seems to permit a peculiar instantaneous connection between particles over long distances that defies the laws of our macroscopic world – a phenomenon that [Albert] Einstein referred to as “spooky action at a distance.”

    Developing protocols to detect and quantify entanglement of many-particle quantum states is a key challenge for current experiments because entanglement becomes very difficult to study when many particles are involved. “We are able to control smaller particle ensembles well, where we can measure entanglement in a relatively straight forward way,” says quantum physicist Philipp Hauke. However, “when we are dealing with a large system of entangled particles, this measurement is extremely complex or rather impossible because the resources required scale exponentially with the system size.

    ”Markus Heyl from the Technical University of Munich, Philipp Hauke and Peter Zoller from the Department of Theoretical Physics at the University of Innsbruck and the Institute for Quantum Optics and Quantum Information (IQOQI) at the Austrian Academy of Sciences in collaboration with Luca Tagliacozzo from the Institute of Photonic Sciences in Barcelona (Spain) have found a new way to detect certain properties of many-particle entanglement independent of the size of the system and by using standard measurement tools.

    Entanglement measurable via susceptibility

    “When dealing with more complex systems, scientists had to carry out a large number of measurements to detect and quantify entanglement between many particles,” says Philipp Hauke. “Our protocol avoids this problem and can also be used for determining entanglement in macroscopic objects, which was nearly impossible until now.”

    Using this new method, physicists can employ tools already well established experimentally. In their study published in Nature Physics the team of researchers gives explicit examples to demonstrate its framework: The entanglement of many-particle systems trapped in optical lattices can be determined using laser spectroscopy while the well-established technique of neutron scattering is utilized for measuring entanglement in solid-state systems.

    The physicists successfully demonstrated that the quantum Fisher information, which can provide reliable proof for genuine multipartite entanglement, is in fact measurable. The researchers emphasize that entanglement can be detected by measuring the dynamic response of a system to a perturbation, which can be determined by comparing individual measurements.

    “For example, when we move a sample through a time-dependent magnetic field, we can determine the system’s susceptibility towards the magnetic field through the measurement data and thereby detect and quantify internal entanglement,” explains Hauke.

    Manifold applications

    Quantum metrology, i.e. measurement techniques with increased precision exploiting quantum mechanics, is not the only important field of application of this protocol. It will also provide new perspectives for quantum simulations, where quantum entanglement is used as a resource for studying properties of quantum systems.

    In solid-state physics, the protocol may be employed to investigate the role of entanglement in many-body systems, thereby providing a deeper understanding of quantum matter. The research work was supported by the European Community, the European Research Council (ERC), the Austrian Science Fund, the Spanish Government and the German National Academy of Sciences Leopoldina.

    Publication:

    Measuring multipartite entanglement via dynamic susceptibilities. Philipp Hauke, Markus Heyl, Luca Tagliacozzo, Peter Zoller. Advanced Online Publication, Nature Physics, on 21 March 2016. – DOI: 10.1038/nphys3700

    See the full article here .

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  • richardmitnick 11:14 am on February 1, 2016 Permalink | Reply
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    From TUM: “Superconductivity in the land of the “heavy fermions” 

    Techniche Universitat Munchen

    Techniche Universitat Munchen

    01.02.2016
    Prof. Dr. Erwin Schuberth
    Technical University Munich
    Chair for Technical Physics (E23)
    Walther-Meißner-Str. 8, 85748 Garching, Germany

    Superconductivity at low temps ytterbium rhodium and silicon.
    Chips of the intermetallic Ytterbium-Rhodium-Silicide (YbRh2Si2) shimmer golden under the microscope. One unit of the superimposed scale corresponds to 0,1 mm. – Photo: Marc Tippmann / TUM

    An international research team has discovered nonclassical superconductivity at extremely low temperatures in a compound of ytterbium, rhodium, and silicon. The project was a collaboration among physicists of the Technical University of Munich (TUM), the Walther Meissner Institute of the Bavarian Academy of Sciences in Garching, the Max Planck Institute for Chemical Physics of Solids in Dresden, Rice University (Houston, USA), and Renmin University (Beijing, China).

    Superconductors transport electrical current completely without resistance and are therefore of high interest for technology. While there is a physical explanation for classical superconductivity, it is not yet clear how the phenomenon comes about in high-temperature superconductors. Researchers worldwide are searching for models and examples that could explain it and bring them closer to the long-term goal of achieving room-temperature superconductivity.

    Now a mechanism by which superconductivity arises at low temperatures in a compound of ytterbium, rhodium, and silicon (YbRh2Si2) has been discovered by an international team: Prof. Erwin Schuberth of TUM and the Walther Meissner Institute of the Bavarian Academy of Sciences, Prof. Frank Steglich, director of the Max Planck Institute for Chemical Physics of Solids in Dresden, Prof. Qimiao Si of Rice University, and Prof. Rong Yu of Renmin University.

    In the land of the “heavy fermions”

    In contrast to neutrons and protons, the building blocks of the atomic nucleus, electrons are extremely light. They belong to the class of particles known as fermions. In special materials and under particular conditions, though, they behave as if they were a thousand times heavier. The intermetallic compound of ytterbium, rhodium, and silicon that the researchers investigated is a typical representative of such a material, a so-called heavy-fermion system.

    “There is already compelling evidence that unconventional superconductivity is linked, in both copper-based and iron-based high-temperature superconductors, to quantum fluctuations that alter the magnetic order of the materials at ‘quantum critical points,’ watershed thresholds that mark the transition from one quantum phase to another,” Qimao Si says. “This work provides the first evidence that similar processes bring about superconductivity in heavy-fermion systems.”

    Ultralow temperatures

    In Frank Steglich’s research group, heavy-fermion systems such as the ytterbium-rhodium-silicide have been intensively studied for more than 15 years. In earlier investigations, an external magnetic field enabled the researchers to obtain quantum fluctuations but inhibited the transition to superconductivity.

    For their new experiments, the scientists used a nuclear demagnetization cryostat at the Bavarian Academy of Science’s Walther Meissner Institute in Garching. This device can cool samples down to a temperature of 400 millionths of a degree Kelvin. At a transition temperature of two millikelvin, the samples suddenly became superconducting.

    In specific-heat measurements, the study’s authors were surprised to see that the effective mass of the charge carriers in their compound appeared to increase by a further factor of 1000 when the material was cooled below the superconducting transition temperature. “That shows clearly that in the domain of ultralow temperatures, interactions with the nuclear spin of the surrounding atoms are at work,” says Erwin Schuberth. “They form a magnetic order that makes superconductivity possible.”

    Nuclear spins rearrange themselves

    When theorists Qimiao Si and Rong Yu analyzed the measurement results, they found that the prerequisite for the superconductivity is a special arrangement of the nuclear spins of the ytterbium. According to their theory, at extremely low temperatures the nuclear spins link up and arrange themselves in a manner that competes with and decisively weakens the antimagnetic electronic order. In this way, the electronic “quantum critical” fluctuations come to bear – the driving force for the superconductivity.

    “This work shows that the emergence of nonclassical superconductivity in the vicinity of antiferromagnetic instabilities is a general phenomenon,” says Frank Steglich. “It is not confined to the cuprates and organic superconductors, but also occurs in the heavy-fermion materials, model substances for quantum materials with extremely strong electronic correlations.”

    This research was supported by the German Research Foundation (DFG), the Robert A. Welch Foundation, and the National Science Foundation (NSF).

    Publication:

    Emergence of superconductivity in the canonical heavy-electron metal YbRh2Si2
    Erwin Schuberth, Marc Tippmann, Lucia Steinke, Stefan Lausberg, Alexander Steppke, Manuel Brando, Cornelius Krellner, Christoph Geibel, Rong Yu, Qimiao Si, Frank Steglich; Science, 29.01.2016 – DOI: 10.1126/science.aaa9733

    See the full article here .

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    Technische Universität München (TUM) is one of Europe’s top universities. It is committed to excellence in research and teaching, interdisciplinary education and the active promotion of promising young scientists. The university also forges strong links with companies and scientific institutions across the world. TUM was one of the first universities in Germany to be named a University of Excellence. Moreover, TUM regularly ranks among the best European universities in international rankings.

     
  • richardmitnick 10:04 am on December 3, 2015 Permalink | Reply
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    From TUM: “Quantum computer made of standard semiconductor materials” 

    Techniche Universitat Munchen

    Techniche Universitat Munchen

    1
    Electron in a quantum dot influenced by the spins in the proximity – Image: Fabian Flassik / TUM

    02.12.2015
    Prof. Jonathan J. Finley
    Walter Schottky Institute
    Technical University of Munich
    85748 Garching; Germany
    Tel.: +49 89 289 11481
    jonathan.finley@wsi.tum.de

    Physicists at the Technical University of Munich, the Los Alamos National Laboratory and Stanford University (USA) have tracked down semiconductor nanostructure mechanisms that can result in the loss of stored information – and halted the amnesia using an external magnetic field. The new nanostructures comprise common semiconductor materials compatible with standard manufacturing processes.

    Quantum bits, qubits for short, are the basic logical elements of quantum information processing (QIP) that may represent the future of computer technology. Since they process problems in a quantum-mechanical manner, such quantum computers might one day solve complex problems much more quickly than currently possible, so the hope of researchers.

    In principle, there are various possibilities of implementing qubits: photons are an option equally as viable as confined ions or atoms whose states can be altered in a targeted manner using lasers. The key questions regarding their potential use as memory units are how long information can be stored in the system and which mechanisms might lead to a loss of information.

    A team of physicists headed by Alexander Bechtold and Professor Jonathan Finley at the Walter Schottky Institute of the Technical University of Munich and the Excellence Cluster Nanosystems Initiative Munich (NIM) have now presented a system comprising a single electron trapped in a semiconductor nanostructure. Here, the electron’s spin serves as the information carrier.

    The researchers were able to precisely demonstrate the existence of different data loss mechanisms and also showed that stored information can nonetheless be retained using an external magnetic field.

    Electrons trapped in a quantum dot

    The TUM physicists evaporated indium gallium arsenide onto a gallium arsenide substrate to form their nanostructure. As a result of the different lattice spacing of the two semiconductor materials strain is produced at the interface between the crystal grids. The system thus forms nanometer-scale “hills” – so-called quantum dots.

    When the quantum dots are cooled down to liquid helium temperatures and optically excited, a singe electron can be trapped in each of the quantum dots. The spin states of the electrons can then be used as information stores. Laser pulses can read and alter the states optically from outside. This makes the system ideal as a building block for future quantum computers.

    Spin up or spin down correspond to the standard logical information units 0 and 1. But, on top of this come additional intermediate states of quantum mechanical up and down superpositions.

    Hitherto unknown memory loss mechanisms

    However, there is one problem: “We found out that the strain in the semiconductor material leads to a new and until recently unknown mechanism that results in the loss of quantum information,” says Alexander Bechtold. The strain creates tiny electric fields in the semiconductor that influence the nuclear spin orientation of the atomic nuclei.

    “It’s a kind of piezoelectric effect,” says Bechthold. “It results in uncontrolled fluctuations in the nuclear spins.” These can, in turn, modify the spin of the electrons, i.e. the stored information. The information is lost within a few hundred nanoseconds.

    In addition, Alexander Bechthold’s team was able to provide concrete evidence for further information loss mechanisms, for example that electron spins are generally influenced by the spins of the surrounding 100,000 atomic nuclei.

    Preventing quantum mechanical amnesia

    “However, both loss channels can be switched off when a magnetic field of around 1.5 tesla is applied,” says Bechtold. “This corresponds to the magnetic field strength of a strong permanent magnet. It stabilizes the nuclear spins and the encoded information remains intact.”

    “Overall, the system is extremely promising,” according to Jonathan Finley, head of the research group. “The semiconductor quantum dots have the advantage that they harmonize perfectly with existing computer technology since they are made of similar semiconductor material.” They could even be equipped with electrical contacts, allowing them to be controlled not only optically using a laser, but also using voltage pulses.

    The research was funded by the European Union (S3 Nano and BaCaTeC), the US Department of Energy, the US Army Research Office (ARO), the German Research Foundation DFG (excellence cluster Nanosystems Munich (NIM) and SFB 631), the Alexander von Humboldt Foundation as well as the TUM Institute for Advanced Study (Focus Group Nanophotonics and Quantum Optics).

    Publication:

    Three-stage decoherence dynamics of an electron spin qubit in an optically active quantum dot; Alexander Bechtold, Dominik Rauch, Fuxiang Li, Tobias Simmet, Per-Lennart Ardelt, Armin Regler, Kai Müller, Nikolai A. Sinitsyn and Jonathan J. Finley; Nature Physics, 11, 1005-1008 (2015) – DOI: 10.1038/nphys3470

    See the full article here .

    Please help promote STEM in your local schools.

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    Technische Universität München (TUM) is one of Europe’s top universities. It is committed to excellence in research and teaching, interdisciplinary education and the active promotion of promising young scientists. The university also forges strong links with companies and scientific institutions across the world. TUM was one of the first universities in Germany to be named a University of Excellence. Moreover, TUM regularly ranks among the best European universities in international rankings.

     
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