Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

"Online First" included
Without submitted and only approved publications
Only approved publications

30259 Publications
Analysis of moulded wood tube structure using gamma-ray computed tomography
Bieberle, A.; Engmann, C.; Hartig, J.; Haller, P.

For the investigation of compressive load moulded wood tube gamma-ray CT has been applied at a 3 m long wood tube at different cross-sectional sections. CT data is normalized to the density of tap water with app. 22 °C temperature.

Keywords: moulded wood tube; gamma-ray computed tomography
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2018-09-18
    DOI: 10.14278/rodare.54

Downloads:

Publ.-Id: 27941 - Permalink


Geometry-induced motion of magnetic domain walls in curved nanostripes
Yershov, K. V.; Kravchuk, V. P.; Sheka, D. D.; Pylypovskyi, O. V.; Makarov, D.; Gaididei, Y.
Dynamics of topological magnetic textures are typically induced externally by, e.g., magnetic fields or spin/charge currents. Here, we demonstrate the effect of the internal-to-the-system geometry-induced motion of a domain wall in a curved nanostripe. Being driven by a gradient of the curvature of a stripe with biaxial anisotropy, transversal domain walls acquire remarkably high velocities of up to 100m/s and do not exhibit any Walker-type speed limit. We pinpoint that the inhomogeneous distribution of the curvature-induced Dzyaloshinskii-Moriya interaction is a driving force for the motion of a domain wall. Although we showcase our approach on the specific Euler spiral geometry, the approach is general and can be applied to a wide class of geometries.

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Publ.-Id: 27939 - Permalink


Convection and mass transfer near a hydrogen bubble evolving during water electrolysis in magnetic fields
Mutschke, G.; Yang, X.; Eckert, K.; Uhlemann, M.; Baczyzmalski, D.; Cierpka, C.
Hydrogen produced from wind or solar power could be used easily for storing energy also at large scale, thus allowing to bridge the gap between supply and demand of renewable energy with respect to time and place. When splitting water by electrolysis, a deeper look at local phenomena near single bubbles at the electrode might be helpful to improve our understanding of this process. In the recent literature, magnetic fields are discussed with respect to the bubble departure, thereby possibly influencing the efficiency of the process [1-5].
The contribution will present numerical simulations resolving in detail local phenomena near a single hydrogen bubble evolving at a small circular cathode during the electrolysis of water. The results are compared with experimental data of hydrogen evolution at a platinum micro-electrode. Hereby, the influence of the Lorentz force caused by vertical and horizontal magnetic fields will be discussed. The results presented will provide insight into electrolyte convection, species concentration, mass transfer and on the bubble departure [6-8].
Keywords: electrolysis, gas evolution, convection, mass transfer, magnetic field, Lorentz force, numerical simulation
  • Lecture (Conference)
    12. European Fluid Mechanics Conference, 09.-13.09.2018, Wien, Österreich

Publ.-Id: 27934 - Permalink


Hydrometallurgy @ HIF
Gutzmer, J.
Hydrometallurgical research of HZDR will be presented in this contribution. .An overview will be provided on relevant hydrometallurgical research carried out in Freiberg and in Dresden. The progress of collaborative research projects will be documented and preliminary results presented. A particular focus will be set on the development of pilot plant-scale research facilities and the opportunities this offers for future research.
Keywords: Hydrometallurgy, HZDR
  • Invited lecture (Conferences)
    BASF Innovation Day, 13.-14.09.2018, Ludwigshafen, Germany

Publ.-Id: 27931 - Permalink


Simulation based LCA – Digitalizing the Circular Economy - Its simulation with two cases: eWaste & batteries/Zn fuming
Reuter, M. A.
Circular Economy (CE)
-The origins
Circular Economy Engineering (CEE)
Metallurgical Internet-of-Things (m-IoT)
-Comprehensive flowsheets that integrate product design with physical separation and process metallurgy
Informing Resource Efficiency (iRE)
-Case 1: Fairphone
-Case 2: Plasma furnace for battery smelting & fuming
Additional Sheets
-Case 3: Recycling of LED lamps / Literature / More detailed sheets
Keywords: Circular Economy, Sustainability, Circular Economy Engineering, thermoeconomics, recycling, Metallurgical Internet of Things, Metal Wheel, Digitalizing
  • Lecture (others)
    HSC 9 Life Cycle Assessment for Process Industry // Training Courses, 03.-05.06.2018, Pori, Finnland

Publ.-Id: 27929 - Permalink


Experimental study of liquid velocity profiles in large-scale bubble columns with particle tracking velocimetry
Besagni, G.; Inzoli, F.; Ziegenhein, T.; Lucas, D.
A complete knowledge of bubble column fluid dynamics relies on understanding both the “global-scale” and the “local-scale” phenomena and coupling between the phases. Unfortunately, most of the previous literature focused on the “global-scale” fluid dynamics, whereas a limited attention was devoted to the “local-scale” fluid dynamics. In this study, we contribute to the present-day discussion through an experimental study concerning the local liquid velocity field in the pseudo-homogeneous flow regime. The experimental study, based on a particle-identification and particle-tracking algorithm, was conducted in a large-diameter and large-scale air-water bubble column (with a height of 5.3 m and inner diameter of 0.24 m) operated in the counter-current mode. We considered gas superficial velocities in the range of 0.37–1.88 cm/s and liquid superficial velocities up to −9 cm/s. The time-averaged and the transient liquid velocity field were obtained and critically discussed for five superficial gas velocities and four superficial liquid velocities at two measuring heights. Subsequently, the local locally resolved information concerning the liquid velocity were coupled with the previously measured bubble size distributions and local void fractions, to provide a complete description of the “local-scale” fluid dynamics. In addition, these data would help in the validation of numerical codes to predict industrial-scale relevant conditions.
Keywords: bubbly column, pilot scale, experiment
  • Contribution to proceedings
    36th UIT Heat Transfer Conference, 25.-27.06.2018, Catania, Italy
  • Lecture (Conference)
    36th UIT Heat Transfer Conference, 25.-27.06.2018, Catania, Italy

Publ.-Id: 27928 - Permalink


Multi-fluid models for gas-liquid flows
Lucas, D.; Krepper, E.; Liao, Y.; Höhne, T.; Rzehak, R.; Schlegel, F.; Ziegenhein, T.
The two- or multi-fluid approach is frequently used for NRS-related simulations of gas-liquid flows. To enable reliable predictions the closure models have to reflect the involved local physical phenomena at the non-resolved scale properly. To consolidate the CFD-modelling in the frame of the multi-fluid approach the so-called baseline model strategy was recently proposed (Lucas et al., 2016). The paper discusses a long-term strategy for the baseline model development and ways to obtain or improve closure models. Guidelines for the model development are given by listing requirements for appropriate closure models as well as frequently made mistakes. This is illustrated by examples for recent developments done for HZDR baseline models for poly-disperse bubbly and segregated flows. Beside an update on recent developments ongoing and planned activities are discussed. Both models are united in the GENTOP-concept which allows simulating flow pattern transitions. Finally, perspectives for the use of OpenFOAM for NRS are discussed.
Keywords: CFD, multiphase, closure model, validation
  • Contribution to proceedings
    OECD/NEA&IAEA CFD4NRS-7 Workshop Application of CFD/CMFD Codes to Nuclear Reactor Safety and Design and their Experimental Validation, 04.-06.09.2018, Shanghai, China
  • Lecture (Conference)
    OECD/NEA&IAEA CFD4NRS-7 Workshop Application of CFD/CMFD Codes to Nuclear Reactor Safety and Design and their Experimental Validation, 04.-06.09.2018, Shanghai, China

Publ.-Id: 27927 - Permalink


High peak currents from a beam loaded nanocoulomb-class laser wakefield accelerator
Couperus, J. P.ORC; Köhler, A.; Zarini, O.; Pausch, R.; Kurz, T.; Krämer, J. M.; Schöbel, S.; Laberge, M.; Hannasch, A.; Zgadzaj, R.; Heinemann, T.; Martinez De La Ossa, A.; Debus, A.; Bussmann, M.; Downer, M.; Schramm, U.; Irman, A.
Laser wakefield accelerators have the capability to produce few-femtosecond, high charge and high peak current beams in the GeV energy range within only a few centimeters of acceleration length. The unique beam properties from these novel concept accelerators can be employed to explore new concepts such as beam driven plasma acceleration or driving superradiant light sources, which require peak currents beyond those found in current conventional accelerators.
Here, we report on robust generation of high quality electron beams at unprecedented high peak currents. The self-truncated ionization injection scheme is employed, enabling a precise control over the amount of injected electrons with charges up to 0.5 nC (FWHM) at a quasi-monoenergetic peak. Minimization of energy spread is reached by optimizing the beam loading condition1,2. An ultrafast single-shot electron beam diagnostic based on Coherent Optical Transition Radiation reveals ~10 femtosecond bunch lengths yielding peak currents of over 10 kA. Such peak currents are one to two orders of magnitude larger than those found in conventional RF accelerators. Control of the energy spread of LWFA beams with the beam loading condition together with the scaling to high peak currents paves the road for driving superradiant lights sources and enables the first proof-of-principle experiment of a hybrid laser- to beam-driven plasma wakefield accelerator in an effort to further improve beam quality found in plasma accelerators.

1 J.P. Couperus et al., “Demonstration of a beam loaded nanocoulomb-class laser wakefield accelerator”, Nature Communication, 8, 487 (2017)
2 A. Irman et al., “Improved performance of laser wakefield acceleration by tailored self-truncation ionization injection”, Plasma Physics and Controlled Fusion, 60, 044015 (2018)
Keywords: Laser Wakefield Acceleration, LWFA, Beam loading, Electron acceleration
  • Lecture (Conference)
    Advanced Accelerators Concepts Workshop, 13.-17.08.2018, Breckenridge, Colorado, USA

Publ.-Id: 27926 - Permalink


Molecular imaging using the theranostic agent 197(m)Hg: phantom measurements and Monte Carlo simulations
Freudenberg, R.ORC; Apolle, R.ORC; Walther, M.; Hartmann, H.; Kotzerke, J.
Background: Radiomercury 197mHg and 197Hg, henceforth referred to as 197(m)Hg, is a promising theranostic radionuclide endowed with properties that allow diagnostic and therapeutic applications. The aim of this work was to investigate the capabilities of 197(m)Hg for nuclear medicine imaging. Therefore measurements were performed by using a Philips BrightView SPECT camera. Furthermore, Monte Carlo simulations using the GATE software were performed to theoretically explore the imaging contribution from the various gamma and X-ray emissions from 197(m)Hg for a commercial clinical camera with low-energy high-resolution (LEHR) and high-energy general-purpose (HEGP) collimators. We estimated the spatial resolution by using a four-quadrant bar phantom, and we evaluated the planar and tomographic images from an abdominal phantom containing three cylindrical sources of 197(m)Hg solution.
Results: A good accordance between measurements and simulations was found for planar and SPECT imaging. Simulations allowed the decomposition of the detected energy spectrum into photon origins. Measurements and simulations for the bar phantom revealed that for the LEHR collimator, the 6-mm pattern could be resolved, whereas for the HEGP collimator, the resolution is about 10 mm. Furthermore, we found that no significant image distortion results from high-energy photons when using the LEHR collimator.
Conclusions: We demonstrated the imaging capabilities of 197(m)Hg which is essential both for diagnostic applications and to determine the in vivo biodistribution for dose calculations in therapeutic applications.
Keywords: GATE, Gamma camera, 197(m)Hg, Monte Carlo simulation, Radiomercury

Downloads:

Publ.-Id: 27925 - Permalink


State of the Art Design for Recycling: Case Fairphone
Reuter, M. A.
- Circular Economy (CE)
- Circular Economy Engineering (CEE)
- Metallurgical Internet-of-Things (m-loT)
- informing Resource Efficieny (iRE) - Fairphone
- Additional Sheets - Recycling of LED lamps/Literature/More detailed sheets
Keywords: Circular Economy, Circular Economy Engineering, Metallurgical Internet-of-Things, Resource Efficieny, Fairphone, Recycling
  • Invited lecture (Conferences)
    Recycling Metals from Industrial Waste - Anual Short Course / Workshop, 26.-29.06.2018, Golden Colorado, USA

Publ.-Id: 27924 - Permalink


Die Digitalisierung der Kreislaufwirtschaft - Wie recyclebar sind Smartphones?
Reuter, M. A.
Circular Economy (CE)
Circular Economy Engineering (CEE)
Metallurgical Internet-of-Things (m-IoT)
informing Resource Efficiency (iRE)
Keywords: Circular Economy, Circular Economy Engineering, Metallurgical Internet-of-Things, Resource Efficiency
  • Lecture (others)
    Intelligente Kreislaufwirtschaft - Aktuelle Aspekte zu Recycling, Aufbereitung und Fernerkundung / Lehrerfortbildung, 16.02.2018, Freiberg, Deutschland

Publ.-Id: 27923 - Permalink


Simulation based footprint of technology
Reuter, M. A.
Overview of Circular Economy in the Metallurgical Processing Industry
Introduction into HSC / into Simulation Based Footprinting / of Case: Processing of slag in a plasma furnace
Completion of Case
Environmental impact assessment using HSC Sim and GaBi
Keywords: Circular Economy, Resource Efficiency, Recycling, Sustainability, Circular Economy Engineering, Fairphone
  • Lecture (others)
    EIT KIC Workshop, 15.-17.05.2018, Freiberg, Deutschland

Publ.-Id: 27922 - Permalink


Thermoeconomic Analysis of a Copper Production Plant - From Mine to Cathode
Reuter, M. A.; Llamasa, A. A.; Stelter, M.; Valero Delgado, A.; Hultgren, M.; Peltomäki, M.; Roine, A.
- Introduction Circular Economy
- Exergy as a resource consumption indicator
- Thermoeconomics
- Simulation-based exergy and thermoeconomic analysis
- Extractive metallurgy of copper case
- Conclusions
Keywords: Circular Economy, Thermoeconomics
  • Invited lecture (Conferences)
    Sustainable Minerals '18 - Towards a circular economy // MEI Conference, 14.-15.06.2018, Windhoek, Namibia

Publ.-Id: 27920 - Permalink


The Circular Economy - Challenges, Opportunities, Limits
Reuter, M. A.
- Circular Economy (CE) + the origins
- Circular Economy Engineering (CEE) + System Integrated Metal Production (SIMP)
- Metallurgical Internet-of-Things (m-loT)
+ Comprehensive flowsheets that integrate product design with physical separation and process metallurgy
+ LED lamps
- informing Resource Efficiency (iRE)
+ Fairphone
Keywords: Circular Economy, Circular Economy Engineering, Metallurgical Internet-of-Things, Resource Efficiency, Fairphone
  • Lecture (others)
    Circular Economy Design Forum, 28.03.2018, Espoo, Finnland

Publ.-Id: 27918 - Permalink


Opportunities and limits of the Circular Econonmy – A metallurgical perspective.
Reuter, M. A.
Rock-to-Metal digitalized and linked to Energy is the Music
The Metal Wheel – A deep understanding is required
Metallurgical Infrastructure Criticality; not only Metal / Element Criticality
Digitalization of the Circular Economy & Analysis
Analyzing the CE system to understand economically the losses on a simulation basis using thermoeconomics & LCA
EU’s Metal Wheel: Develop thermodynamic detail
The Limits of Recycling: Modular design pushing limits
Keywords: Exergy, LCA, thermo-economics, Fairphone, Digitalization
  • Invited lecture (Conferences)
    12th Society And Materials International Conference - SAM 12, 22.-23.05.2018, Metz, Frankreich

Publ.-Id: 27915 - Permalink


No growth without raw materials: Europe must maintain and develop production and recycling technologies.
Reuter, M. A.
The aim of the seminar should be to define the role of regions in shaping a holistic industrial strategy for the EU, particularly with regard to innovation, digitalisation and global competition.
Through a smart, sustainable and inclusive industrial policy, innovative ecosystems are to be promoted in the regions, entrepreneurship encouraged, and jobs created.
Regulatory barriers will need to be dismantled, sustainability ensured, European technological sovereignty preserved and fairness achieved in global competition. To this end, the experience and knowledge of the regions and their proposals for a future EU industrial strategy are indispensable.
The example of Saxony can be used to demonstrate the progress made towards “Industry 4.0” in the fields of microelectronics, e-mobility, material efficiency/resource technologies and advanced manufacturing.
  • Invited lecture (Conferences)
    ECON external Seminar on "Shaping change — towards a holistic industrial strategy", 02.-03.05.2018, Dresden, Deutschland

Publ.-Id: 27914 - Permalink


Simulation based life cycle assessment of metallurgical and recycling processes
Reuter, M. A.
Process simulation and environmental softwareare applied to quantify resource efficiency (RE) in a rigorous manner. These digitalisation tools are linked and will be used to show how the environmental performance of copper primary production, the processing of residues and the recycling of e-waste, e.g. light emitting diode (LED) lamps as well as the production of nickel pig iron can be evaluated.
Keywords: HSC, design for recycling, Fairphone, process simulation, recyclability
  • Invited lecture (Conferences)
    Life Cycle Assessment Symposium, 27.04.2018, Freiberg, Deutschland

Publ.-Id: 27911 - Permalink


Limits of the circular economy: Fairphone modular design pushing the limits
Reuter, M. A.; Ballester, M.; van Schaik, A.
The limitations to materials flows from recycling in the circular economy are discussed using as a case a simulation-based analysis of the recyclability of the Fairphone 2. Three different recycling routes are analysed using simulation models that link the bill of materials and full material declarations to the final metal recovery via physical separation models. The recycling and recovery rates are depicted in an innovative recycling index and material flower that helps drive the discussion about the inevitable tradeoffs between the recyclability of different target materials and debunks the myth of a total recyclability of materials. Modular design is shown to have clear recycling as well as environmental advantages. This study is part of the SustainablySMART project.This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 680640. © 2018 GDMB Gesellschaft fur Bergbau, Metallurgie, Rohstoff- und Umwelttechnik e.V. All rights reserved.
Keywords: Circular economy, Design for recycling, Fairphone, Recycling-index, Simulation
  • Invited lecture (Conferences)
    Sustainable Minerals '18 - Towards a circular economy // MEI Conference, 14.-15.06.2018, Windhoek, Namibia

Publ.-Id: 27909 - Permalink


The (Geo) Metallurgy of the Circular Economy
Reuter, M. A.
Circular economy (CE) is defined here in terms of the metallurgical Internet of Things (m-IoT). This is the digitalized Web of Metals (WoM) or, in other words, the system integrated material production (SIMP). Its digitalization provides the real-time detail that quantifies the three pillars of sustainability: social, environmental, and economical. This is termed ‘‘circular economy engineering’’ (CEE), i.e., the digitalization of the CE, using among others the theory and technology of minerals processing, metallurgy, recycling, computer-aided engineering (CAE), and product design. This provides the basis for the estimation of the metrics of resource efficiency (RE) and, hence, provides a direction for innovation and also enables the m-IoT.

#Geometallurgy18
Geometallurgy is now largely accepted as the process to quantify and understand a mineral deposit in terms of its structure, composition and ultimately to determine its economic value.
Geometallurgy 2018 will bring together experts from academia and industrial research, practitioners from operating mines, consultants and contractors as well as industry bodies with the aim of increasing the understanding and value of mineral assets.
Keywords: Circular economy, digitalization, metallurgy, recycling, resource efficiency
  • Invited lecture (Conferences)
    GEOMETALLURGY 2018, 19.-20.04.2018, London, Großbritannien

Publ.-Id: 27906 - Permalink


Directionality of nickel-induced layer exchange during graphitization in carbon-nickel thin films
Janke, D.; Wenisch, R.; Munnik, F.; Hübner, R.; Grenzer, J.; Gemming, S.; Rafaja, D.; Krause, M.
Metal-induced crystallization with layer exchange (MIC w LE) can reduce the crystallization temperature of group 14 elements by several hundred degrees. This is especially interesting for device fabrication on substrates with limited thermal stability. Ideally, the process allows the transfer of defined amounts of an initially amorphous material onto a randomly selected substrate. In this contribution, MIC w LE is studied for Ni/ a-C thin films with different stacking sequences in order to quantify the influence of the stacking sequence on the layer exchange degree αLE and on the degree of graphitic ordering. The process was monitored in situ by temperature-dependent Rutherford backscattering spectrometry (RBS) and Raman spectroscopy up to 700 °C. RBS, Raman, elastic recoil detection, X-ray diffraction and transmission electron microscopy were applied for ex situ characterization.
The highest αLE of 96% was found for the initial Ni/a-C stacking sequence. In contrast, the inverse sequence resulted in an incomplete LE. The formation of 2D-layered carbon structures occurred independently of the initial stacking sequence.1 Beyond the threshold of 580 °C, increasing the temperature to up to 700 °C had a negligible impact on the degree of 2D-ordering. Since LE and graphitization occur simultaneously at high temperatures, MIC w LE rather than dissolution/ precipitation is proposed as responsible mechanism for carbon crystallization.
Keywords: metal-induced crystallization, directionality, amorphous carbon, nickel, graphitization, layer exchange, ERD, Raman, TEM
  • Lecture (Conference)
    Flatlands 2018, 03.-07.09.2018, Leipzig, Deutschland

Publ.-Id: 27903 - Permalink


Digitalizing the Circular Economy - Metallurgical process system is the carrier
Reuter, M. A.
Metallurgy is a key enabler of a circular economy (CE), its digitization is the metallurgical Internet of Things (m-IoT). In short: Metallurgy is at the heart of a CE, as metals all have strong intrinsic recycling potentials. Process metallurgy, as a key enabler for a CE, will help much to deliver its goals. The first-principles models of process engineering help quantify the resource efficiency (RE) of the CE system, connecting all stakeholders via digitization. This provides well-argued and first-principles environmental information to empower a tax paying consumer society, policy, legislators, and environmentalists. It provides the details of capital expenditure and operational expenditure estimates. Through this path, the opportunities and limits of a CE, recycling, and its technology can be estimated. The true boundaries of sustainability can be determined in addition to the techno-economic evaluation of RE. The integration of metallurgical reactor technology and systems digitally, not only on one site but linking different sites globally via hardware, is the basis for describing CE systems as dynamic feedback control loops, i.e., the m-IoT. It is the linkage of the global carrier metallurgical processing system infrastructure that maximizes the recovery of all minor and technology elements in its associated refining metallurgical infrastructure.
Keywords: circular economy, digitization, recycling, resource efficiency, sustainability
  • Invited lecture (Conferences)
    8th Forum of Non-Ferrous Metals, 21.-23.02.2018, Krakau, Polen

Publ.-Id: 27902 - Permalink


Digitalizing the Circular Economy - Fairphone as example
Reuter, M. A.
The limitations to materials flows from recycling in the circular economy are discussed using as a case a simulation-based analysis of the recyclability of the Fairphone 2. Three different recycling routes are analysed using simulation models that link the bill of materials and full material declarations to the final metal recovery via physical separation models. The recycling and recovery rates are depicted in an innovative recycling index and material flower that helps drive the discussion about the inevitable trade-offs between the recyclability of different target materials and debunks the myth of a total recyclability of materials. Modular design is shown to have clear recycling as well as environmental advantages. This study is part of the SustainablySMART project.
Keywords: Circular Economy – Design for Recycling – Fairphone – Simulation – Recycling-Index
  • Invited lecture (Conferences)
    Circular Materials Conference, 07.-08.03.2018, Göteborg, Schweden

Publ.-Id: 27901 - Permalink


Simulation based Design for Recycling - Fairphone as an example
Reuter, M. A.
The limitations to materials flows from recycling in the circular economy are discussed using as a case a simulation-based analysis of the recyclability of the Fairphone 2. Three different recycling routes are analysed using simulation models that link the bill of materials and full material declarations to the final metal recovery via physical separation models. The recycling and recovery rates are depicted in an innovative recycling index and material flower that helps drive the discussion about the inevitable tradeoffs between the recyclability of different target materials and debunks the myth of a total recyclability of materials. Modular design is shown to have clear recycling as well as environmental advantages. This study is part of the SustainablySMART project.
Keywords: Circular Economy – Design for Recycling – Fairphone – Simulation – Recycling-Index
  • Invited lecture (Conferences)
    Berliner Recycling- und Rohstoffkonferenz, 19.03.2018, Berlin, Deutschland

Publ.-Id: 27900 - Permalink


Data Analysis and Machine Learning at the Computational Science Group
Kelling, J.
In this talk I will summarize the current activities of the computational science group at HZDR, which range from establishing research data publication (RODARE) and management platforms to providing numerical and computational expertise in various research projects. The latter aspect will be presented in detail through two selected ongoing projects.

In a project with the institute for resource ecology at HZDR, we developed a framework for the analysis of spectra of mixed solutions. The goal of the analysis is to discover how many species are in a given sample and in what concentration while at the same time extracting their unknown spectrum. A number of numerical techniques can be employed to this end, each requiring different amounts prior knowledge and different types of measurements. Here the primary task of the analysis framework is to unify a zoo of different implementations of similar methods and making all methods available to all scientists. Additionally, it enables simple use of remote computing resources, which allow for more computationally intensive analysis which can add a more reliable way to estimate confidence bounds.

In another project, we are using deep learning approaches to develop an automated safety system for the high-power laser systems DRACO and PENELOPE at HZDR. Here the goal is to detect defects or scatterers which focus parts of a yet unfocussed beam. These can, when left unchecked, cause cascades of failing mirrors, lenses, and non-linear crystals and should thus be detected in the time between two shots. This work uses deep convolutional neural networks implemented through the Caffe framework to achieve real-time detection and localization of impurities in the beam profile.
Keywords: computational science, data management, machine learning
  • Lecture (Conference)
    IHRS NanoNet Annual Workshop, 05.-07.09.2018, Bad Gottleuba, Deutschland

Publ.-Id: 27897 - Permalink


Extended Infrared Photoresponse in Te-Hyperdoped Si at Room Temperature
Wang, M.ORC; Berencén, Y.; García-Hemme, E.; Prucnal, S.; Hübner, R.; Yuan, Y.; Xu, C.; Rebohle, L.; Böttger, R.; Heller, R.; Schneider, H.; Skorupa, W.; Helm, M.; Zhou, S.
Presently, silicon photonics requires photodetectors that are sensitive in a broad infrared range, can operate at room temperature, and are suitable for integration with the existing Si-technology process. Here, we demonstrate strong room-temperature sub-band-gap photoresponse of photodiodes based on Si hyperdoped with tellurium. The epitaxially recrystallized Te-hyperdoped Si layers are developed by ion implantation combined with pulsed-laser melting and incorporate Te-dopant concentrations several orders of magnitude above the solid solubility limit. With increasing Te concentration, the Te-hyperdoped layer changes from insulating to quasi-metallic behavior with a finite conductivity as the temperature tends to zero. The optical absorptance is found to increase monotonically with increasing Te concentration and extends well into the mid-infrared range. Temperature-dependent optoelectronic photoresponse unambiguously demonstrates that the extended infrared photoresponsivity from Te-hyperdoped Si p-n photodiodes is mediated by a Te intermediate band within the upper half of the Si band gap. This work contributes to pave the way toward establishing a Si-based broadband infrared photonic system operating at room temperature.

Downloads:

Publ.-Id: 27886 - Permalink


Hydrodynamic analysis in a viscous coupling using angle-resolved gamma-ray computed tomography
Bieberle, A.; Spies, A.; Schlottke, J.

This work comprises data provided by high-resolution gamma-ray computed tomography that was applied on a viscous coupling to visualize the internal operating fluid distribution. Therefore, angle-resolved time-averaged CT scanning technique was performed at different

  • cross-sectional positions,
  • rotational speeds as well as
  • at primary and secondary side. 

Keywords: viscous coupling; gamma-ray CT; process-synchronized fast imaging
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2018-09-05
    DOI: 10.14278/rodare.49

Downloads:

Publ.-Id: 27884 - Permalink


Activity-Based Probes for Tumour-Associated Transglutaminase 2: From Potent and Selective Inhibitors to Radiotracers
Löser, R.
The talk is covering the efforts of our group in the development of inhibitor-based radiotracers for the imaging of tumour-associated transglutaminase 2 (TGase 2). Major emphasis will be put on interesting structure-activity relationships of N6-acryloyllysine-derived inhibitors. In addition, general principles for targeting of TGase 2 by irreversible inhibitors will be highlighted. Labelling of these compounds with fluorine-18 and initial results towards their radiopharmacological evaluation will be presented.
  • Invited lecture (Conferences)
    Gordon Research Conference "Transglutaminases in Human Disease Processes", 17.-22.06.2018, Les Diablerets, Schweiz

Publ.-Id: 27883 - Permalink


Cathepsin B-Activatable Cell-Penetrating Peptides for Imaging Cancer-related Cathepsin B
Kuhne, K.; Behring, L.; Belter, B.; Wodtke, R.; von Krüchten, L.; Keller, M.; Steinbach, J.; Pietzsch, J.; Löser, R.
In our understanding of the many drivers of malignant progression and cancer metastasis, proteases are increasingly drawn into the spotlight as crucial agents in cancer angiogenesis, invasion, and metastasis [1]. Elevated activities of multiple members of the cathepsin family have been shown to correlate with increased metastasis and high therapy resistance [2, 3]. Especially high expression levels of extracellular cathepsin B (CTB) indicate poor prognosis in neoplastic diseases, making CTB an interesting target for activity-based molecular imaging in diagnostics as well as in therapy monitoring for personalised therapies.
It is our aim to develop such a probe by combination of a polyarginine-based, activatable cell penetrating peptide (ACPP), as first described by R. Tsien, and an optimised endopeptidase substrate for CTB [4]. Substrate optimisation proofed to be challenging as two entirely opposite factors needed to be balanced – high stability against serum proteases to prevent premature cleavage of the activation sequence, while retaining efficient and specific endoproteolytic cleavability by CTB.
We have generated a CTB-endoprotease substrate by C-terminally elongating the CTB carboxydipeptidase substrate Abz GIVR*AK(Dnp) OH (Abz - aminobenzoyl, Dnp – dinitrophenyl, * – cleavage site), described by Cotrin et al. in 2004, to the octapeptide Abz GIVR*AK(Dnp)GX CONH2, which could be used as activation site in the final ACPP [5]. Introduction of any amino acid other than glycine at the P4’ position resulted in hysteretic kinetics for the CTB-catalysed hydrolysis of the octapeptides, which might indicate the displacement of the occluding loop from the active site upon interaction with the substrates. Using LC-ES-MS-based analysis of serum-incubated substrates, the positions P1 and P3’ were determined to be primary determinants of serum stability. After suppression of the P3’ instability by Nα-methylation and optimisation within the positions P1-P3, we were able to increase serum half-life from < 5 min to > 1440 min under concomitant improvement of kinetic substrate efficiency towards CTB.
Currently, the substrate is optimised towards CTB-specificity within the cathepsin protease family. Additionally, cell uptake studies of a fluorescently labelled ACPP using the optimised CTB-endoprotease substrate sequence are ongoing. Using this fluorescent probe, we plan to study cell uptake, in vivo stability and initial biodistribution. Furthermore, an ACPP conjugated to radiometal-chelating entities is currently prepared, which will allow for PET imaging in vivo.

Literature
(1) Yang et al., Cancer Growth Metastasis 2009, 2, 13-27
(2) Aggarwal and Sloane, Proteomics Clin. Appl. 2014, 8(5-6), 427-437
(3) Löser and Pietzsch, Front. Chem. 2015, 3, article 37
(4) Jiang et al., PNAS, 2004, 101(51), 17867-17872
(5) Cotrin et al., Anal. Biochem. 2004, 335, 244-252
  • Lecture (Conference)
    35th European Peptide Symposium, 26.-31.08.2018, Dublin, Irland

Publ.-Id: 27879 - Permalink


Peptidbasierte Rückgewinnung von Gallium aus Abwässern der Halbleiterindustrie
Schönberger, N.; Braun, R.; Matys, S.; Flemming, K.; Lehmann, F.; Lederer, F.; Pollmann, K.
Gallium (Ga) ist wichtiger Bestandteil vieler Halbleiterprodukte und wird in LEDs und Photovoltaikelementen verwendet. Trotz eines stetig wachsenden Bedarfs und endlicher Ressourcen, fehlen Strategien für seine Rückgewinnung aus sekundären Rohstoffquellen. Abfälle aus der Halbleiterindustrie könnten eine ergiebige Quelle für die Gewinnung von hochreinem Ga sein. Der gezielte Einsatz von spezifischen Peptiden ermöglicht die selektive Abtrennung von Metallionen für die Gewinnung von Reinststoffen. Durch das sogenannte „Phagen Display“ können derartige Peptide selektiert werden. Hier wurde die Technik zur Identifizierung Ga-bindender Peptide angewendet.
Es konnten 5 hoch affine Peptide identifiziert werden, die in Einzelklonexperimenten charakterisiert wurden. Hierfür wurde die Fähigkeit der Klone, freie Galliumionen in wässriger Lösung zu sorbieren, untersucht. Alle 5 Klone zeigten im Vergleich zu einem Kontrollphagen eine verbesserte Biosorption von Ga. Bei 2 der 5 Klone wurde eine deutlich höhere Affinität für Ga gegenüber As festgestellt. In weiterführenden Experimenten wurden die metallbindenden Eigenschaften beider Peptide charakterisiert. Durch ein zusätzliches Cystein am C-Terminus lassen sich diese Peptide auf verschiedenen Oberflächen immobilisieren. Auf diese Weise können Materialien zur selektiven Gewinnung von Gallium aus industriellen Abwässern generiert werden.
Keywords: Gallium, Peptide, Phage Display, Biosorption
  • Contribution to proceedings
    ProcessNet-Jahrestagung und 33. DECHEMA-Jahrestagung der Biotechnologen 2018, 10.-12.09.2018, Aachen, Deutschland
    Chemie Ingenieur Technik; Volume 90, Issue 9; Special Issue: ProcessNet‐Jahrestagung und 33. DECHEMA‐Jahrestagung der Biotechnologen 2018, Weinheim, Deutschland: Wiley-VCH Verlag GmbH & Co. KGaA, 0009-286X, 1287-1288
    DOI: 10.1002/cite.201855340

Publ.-Id: 27876 - Permalink


Peptide-based recovery of gallium
Schönberger, N.; Braun, R.; Lehmann, F.; Flemming, K.; Matys, S.; Lederer, F.; Pollmann, K.
High-tech metals are almost ubiquitous in our everyday lives. Due to their great importance for the electronics industry, the demand is continuously growing. The supply of these important raw materials is currently mainly covered by primary raw material sources. However, with increasing technological progress, the supply situation on the global market becomes tense. The recovery of high-tech metals from secondary raw material sources could help to ease the situation. This task is a major challenge due to a strongly mixed matrix and sometimes low concentrations of valuable metals from such sources. However, highly innovative strategies are required to meet this challenge. Modern biotechnology offers promising concepts for the efficient, economical and sustainable recycling of high-tech metals [1].
Recently we’ve established a phage display technology platform for the highly specific recognition of mineral particles as well as of metal ions in polluted water streams. This is escorted by a newly developed system for the heterologous expression of identified peptides [2-4].
Here we report in detail about the development of high-affinity peptide ligands for the recovery of gallium from industrial wastewater. Various gallium binding peptide sequences were identified by applying a commercial dodecamer peptide library (Ph.D.-12, NEB, US). Biopanning conditions were optimized for the enrichment of metal ion binding phage clones, which allows a more precise selection process. By single clone binding studies and competitive binding experiments, 3 sequences were characterized to show high binding affinity and selectivity for gallium above other metals, especially arsenic.
Gallium binding peptides are now produced for further spectroscopic characterization and evaluation of binding properties. In addition immobilization strategies to create peptide-based materials for the recovery of gallium binding peptides will be discussed.

[1] K. Pollmann, S. Kutschke, S. Matys, J. Raff, G. Hlawacek, F.L. Lederer, Bio-recycling of metals: Recycling of technical products using biological applications, Biotechnology Advances, (2018)
[2] R. Braun, S. Matys, N. Schönberger, F.L. Lederer, K. Pollmann, Simplified Expression and Production of Small Metal Binding Peptides, Solid State Phenomena, (2017)
[3] S. Matys, F.L. Lederer, N. Schönberger, R. Braun, F. Lehmann, K. Flemming, S. Bachmann, S. Curtis, R.T.A. MacGillivray, K. Pollmann, Phage Display - A Promising Tool for the Recovery of Valuable Metals from Primary and Secondary Resources, Solid State Phenomena, (2017)
[4] F.L. Lederer, S.B. Curtis, S. Bachmann, W.S. Dunbar, R.T. MacGillivray, Identification of lanthanum-specific peptides for future recycling of rare earth elements from compact fluorescent lamps, Biotechnol Bioeng, (2017)
Keywords: Gallium, Phage display, peptides, biosorption
  • Poster
    35th European Peptide Symposium, 35EPS, 26.-31.08.2018, Dublin, Irland

Publ.-Id: 27875 - Permalink


A forward look into the US rare-earth industry; How potential mines can connect to the global REE market
Barakos, G.; Mischo, H.; Gutzmer, J.
It has been nearly eight years since rare-earth elements (REE) became the subject of front-page headlines. It was when the controversial Chinese export policy for these critical commodities was epitomized in a maritime border dispute with Japan in September 2010 that resulted in the big REE crisis and price spike of 2011 (Barakos et al., 2016c; Mancheri, 2015). The world was dismayed, especially in REE-importing countries such as the United States that was, and still is, totally dependent on Chinese production and exports (Barakos et al, 2016c; Kennedy, 2015). The short-lived alarm initiated a treasure hunt by way of exploration for REE deposits all over the world. The continuously growing demand on the one hand, and the Chinese sovereignty of the REE-market on the other, led the rest of the world to explore their own REE resources. In just a few years, more than 400 projects were initiated to explore REE deposits outside of China
Keywords: REE, USA, Mining, Resource Policy
  • Mining Engineering 70(2018)8, 30-37

Publ.-Id: 27874 - Permalink


Development of Ga binding Peptides using Phage Display Technology
Schönberger, N.; Matys, S.; Lederer, F.; Pollmann, K.
Gallium is a strategically important metal for the German high-tech industry. It is used essentially in the semiconductor compounds GaAs, GaN or GaP for high-potential future technologies. This is offset by low recycling rates and declining availability on the world market. Therefore, the development of processes for the selective recovery of gallium from secondary raw material sources is a desirable starting point for dealing with the increasing scarcity of this resource on the world market. Particularly interesting is the development of a biotechnological method for selective biosorption by using the Phage Surface Display Technology.
This is a well-established method for the selection of highly specific peptide ligands in medicine and biotechnology. Random, short peptide sequences are presented on the surface according to genetically modified bacteriophages. In a biopanning called process, a pool of different bacteriophage is selected against a particular target, thereby enriching specific binding clone variants. A very effective method has been established for the selection of different phage display libraries. Gallium ions immobilized on a monolithic ion exchanger are made accessible for biopanning in an FPLC system. This chromatopanning allows the selective enrichment of gallium-binding clone variants under strictly controlled process conditions.
In the present study, we report about the enrichment, identification and characterization of several gallium-binding peptide motifs. Some promising gallium binding bacteriophage clones are chosen for further binding studies, including bacteriophage immobilization for real waste water treatment experiments.
The corresponding peptide sequences can be synthesized and used in subsequent experiments to characterize metal-peptide interactions and develop biosorptive materials for selective gallium recovery from industrial waste waters.
Keywords: Phage Display, Gallium, Peptides, Biosorption
  • Poster
    4th EURO bio-inspired materials 2018, 19.-22.03.2018, Potsdam, Deutschland

Publ.-Id: 27873 - Permalink


The Implementation of an Activated Temperature Dependent Wall Boiling Model in an Eulerian-Eulerian Computational Fluid Dynamic Approach for Predicting the Wall Boiling Process
Ding, W.; Krepper, E.; Hampel, U.
In this work, we report on a development of time averaged Eulerian multiphase approach applied in the wall boiling process especially in the forced convective boiling process. Recently in order to get accurate bubble dynamics and reduce the case dependency, a single bubble model for nucleate boiling based on the known published models was developed. The model considers geometry change and dynamic contact and inclination angles during the bubble growth. The model has a good agreement with experiments. However the predicted bubble dynamics is wall superheat (cavity activation temperature) dependent. This single bubble model requires an update of the current nucleation site activation and heat partitioning models in time averaged Eulerian multiphase approaches. In this work, we will introduce this implementation in detail. Further with help of the multiple size group (MUSIG) model and a breakup and coalescence model, the time averaged Eulerian approach could simulate the bubble size distribution in a heated pipe. With the necessary calibration of the nucleation site density the comparisons between the calculation results and the Bartolomej’s experiments demonstrate the success of the implementation and the accuracy of this approach.
Keywords: Wall boiling; Eulerian multi-phase approach; microlayer; cavity group activation; updated heat partitioning

Publ.-Id: 27872 - Permalink


Diagnostics for plasma-based electron accelerators
Downer, M.  C.; Zgadzaj, R.; Debus, A.ORC; Schramm, U.ORC; Kaluza, M.  C.
Plasma-based accelerators that impart energy gain as high as several GeV to electrons or positrons within a few centimeters have engendered a new class of diagnostic techniques very different from those used in connection with conventional radio-frequency (rf) accelerators. The need for new diagnostics stems from the micrometer scale and transient, dynamic structure of plasma accelerators, which contrasts with the meter scale and static structure of conventional accelerators. Because of this micrometer source size, plasma-accelerated electron bunches can emerge with smaller normalized transverse emittance (εn<0.1  mm mrad) and shorter duration (τb∼1  fs) than bunches from rf linacs. Single-shot diagnostics are reviewed that determine such small εn and τb noninvasively and with high resolution from wide-bandwidth spectral measurement of electromagnetic radiation the electrons emit: εn from x rays emitted as electrons interact with transverse internal fields of the plasma accelerator or with external optical fields or undulators; τb from THz to optical coherent transition radiation emitted upon traversing interfaces. The duration of ∼1  fs bunches can also be measured by sampling individual cycles of a copropagating optical pulse or by measuring the associated magnetic field using a transverse probe pulse. Because of their luminal velocity and micrometer size, the evolving structure of plasma accelerators, the key determinant of accelerator performance, is exceptionally challenging to visualize in the laboratory. Here a new generation of laboratory diagnostics is reviewed that yield snapshots, or even movies, of laser- and particle-beam-generated plasma accelerator structures based on their phase modulation or deflection of femtosecond electromagnetic or electron probe pulses. Spatiotemporal resolution limits of these imaging techniques are discussed, along with insight into plasma-based acceleration physics that has emerged from analyzing the images and comparing them to simulated plasma structures.
Keywords: Beam diagnostics, Electrostatic waves & oscillations, Laser driven electron acceleration, Laser wakefield acceleration, Particle acceleration in plasmas, Radiation & particle generation in plasmas

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Publ.-Id: 27870 - Permalink


Localization of magnon modes in a curved magnetic nanowire
Gaididei, Y.; Kravchuk, V. P.; Mertens, F. G.; Pylypovskyi, O. V.; Saxena, A.; Sheka, D. D.; Volkov, O. M.
Spin waves in magnetic nanowires can be bound by a local bending of the wire. The eigenfrequency of a truly local magnon mode is determined by the curvature: a general analytical expression is established for any infinitesimally weak localized curvature of the wire. The interaction of the local mode with spin waves, propagating through the bend, results in scattering features, which is well confirmed by spin-lattice simulations.
Keywords: magnetic wire, curvature, local mode, spin wave

Publ.-Id: 27869 - Permalink


Geostatistical Simulation of Geochemical Compositions in the Presence of Multiple Geological Units: Application to Mineral Resource Evaluation
Talebi, H.; Mueller, U.; Tolosana-Delgado, R.; van den Boogaart, K. G.
An accurate prediction of benefit in ore deposits with heterogeneous spatial variations requires the definition of geological domains that differentiate the types of mineralogy, alteration, and lithology, as well as the prediction of full mineral and geochemical compositions within each modeled domain and across boundaries between different domains. This paper proposes and compares various approaches (different combinations of log-ratio transformation, Gaussian and flow anamorphosis, and deterministic or probabilistic geological models) for geostatistical simulation of geochemical compositions in the presence of several geological domains. Different approaches are illustrated through an application to a nickel–cobalt laterite deposit located in Western Australia. Four rock types (ferruginous, smectite, saprolite, and ultramafic) are considered to define compositionally homogeneous domains. Geochemical compositions are comprised of six different components of interest (Fe, Al, Mg, Ni, Co, and Filler). The results suggest that the flow anamorphosis is a vital element for geostatistical modeling of geochemical composition due to its invariance properties and capability for reproducing complex patterns in input data, including: presence of outliers, presence of several populations (due to the presence of several geological domains), nonlinearity, and heteroscedasticity.
Keywords: Compositional data; Log-ratio; Flow anamorphosis; Geostatistical simulation; Geological domaining

Publ.-Id: 27863 - Permalink


LSC-Anwendungen beim Rückbau von Kernkraftwerken
Barkleit, A.ORC
Vorstellung FORKA-Projektskizzen
  • Lecture (Conference)
    LSC-Anwendertreffen, 11.-12.09.2018, Hannover, Deutschland

Publ.-Id: 27861 - Permalink


Integration of Terrestrial and Drone-Borne Hyperspectral and Photogrammetric Sensing Methods for Exploration Mapping and Mining Monitoring
Kirsch, M.; Lorenz, S.; Zimmermann, R.; Tusa, L.; Möckel, R.; Hödl, P.; Booysen, R.; Khodadadzadeh, M.; Gloaguen, R.
Mapping lithology and geological structures accurately remains a challenge in difficult terrain or in active mining areas. We demonstrate that the integration of terrestrial and drone-borne multi-sensor remote sensing techniques significantly improves the reliability, safety, and efficiency of geological activities during exploration and mining monitoring. We describe an integrated workflow to produce a geometrically and spectrally accurate combination of a Structure-from-Motion Multi-View Stereo point cloud and hyperspectral data cubes in the visible to near-infrared (VNIR) and short-wave infrared (SWIR), as well as long-wave infrared (LWIR) ranges acquired by terrestrial and drone-borne imaging sensors. Vertical outcrops in a quarry in the Freiberg mining district, Saxony (Germany), featuring sulfide-rich hydrothermal zones in a granitoid host, are used to showcase the versatility of our approach. The image data are processed using spectroscopic and machine learning algorithms to generate meaningful 2.5D (i.e., surface) maps that are available to geologists on the ground just shortly after data acquisition. We validate the remote sensing data with thin section analysis and laboratory X-ray diffraction, as well as point spectroscopic data. The combination of ground- and drone-based photogrammetric and hyperspectral VNIR, SWIR, and LWIR imaging allows for safer and more efficient ground surveys, as well as a better, statistically sound sampling strategy for further structural, geochemical, and petrological investigations.
Keywords: hyperspectral imaging; Structure-from-Motion (SfM); mineral mapping; virtual outcrops; geology; hydrothermal; UAV; long-wave infrared

Publ.-Id: 27853 - Permalink


Metal oxide double layer capacitors by electrophoretic deposition of metal oxides. Fabrication, electrical characterization and defect analysis using positron annihilation spectroscopy
Hoffmann, R. C.; Koslowski, N.; Sanctis, S.ORC; Liedke, M. O.; Wagner, A.ORC; Butterling, M.; Schneider, J. J.ORC
Films consisting of nanocrystalline ZnO were deposited on ITO/glass electrodes using an electrophoretic process. The microwave-assisted thermolysis of zinc alkyl-acetoacetates resulted in the formation of stable dispersions for the electrophoretic deposition procedure. Uniform and smooth coatings could be achieved by starting the electrophoresis at lower voltages first and increasing to higher voltages at later stages of the deposition. The ZnO/ITO double layers were integrated in metal oxide semiconductor (MOS) capacitors by completing the set-up with a spin-coated PMMA dielectric layer and gold contacts. The MOS capacitors showed IV curves with a region of negative differential resistance, indicating charge trapping, both in the ZnO grains and at the ZnO/PMMA interface. Doppler broadening positron annihilation (DB-PAS) and positron annihilation life time spectroscopy (PALS) were employed to characterize the point defects and void space within the deposited ZnO layer which allowed to give insight into the bulk composition of the film composition. PALS revealed the presence of micropores in the range of 0.5 to 1.5 nm.
Keywords: positron annihilation spectroscopy electrophoretic deposition defect analysis

Publ.-Id: 27852 - Permalink


Post-Younger Dryas fault instability and deformations on ice lineations in Finnish Lapland
Sutinen, R.; Andreani, L.; Middleton, M.
The Younger Dryas phase, which occurred between 12.8 and 11.5 ka as a part of the cyclic pattern of global climatic changes, was concurrent with maximum fault instability (13–10 ka) in the Fennoscandian shield. Ice lineations, indicative of glacial streaming toward the Younger Dryas end moraines (YDEMs), may have faced earthquake impacts within the glacial isostatic adjustment (GIA). Morphometric analyses for airborne laser scanning (ALS) revealed that ice lineations were deformed subglacially and subaerially in Finnish Lapland. The subglacial water outburst flows diagonally eroded the drumlins, 50 km from the YDEMs in Utsjoki, northern Finnish Lapland. Similarly north, in the Sevetti area, 40 km from the YDEMs a large portion of the ice lineations were entirely distorted by the subglacial squeeze-up Pulju moraine and liquefaction bowl formations. In the interior part of the Fennoscandian Ice sheet (FIS) in Kemijärvi, representing onset of an ice-stream fan 200 km from the YDEMs, mass flows had reworked the ice lineations. Based on the electrical-sedimentry anisotropy, mass flow sediments deviated from the ice flow pattern. Postglacial liquefaction craters were created on the drumlins in Utsjoki and also in Kuusamo, eastern Finnish Lapland, 70 km from the YDEMs in Russian Karelia. We interpret these features as indications of paleoseismic events associated with GIA.
Keywords: Lidar DEM, Pulju moraine, Liquefaction, Mass flow

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Publ.-Id: 27851 - Permalink


Irradiation effects on the structural and optical properties of single crystal β-Ga2O3
Liu, C.; Berencén, Y.; Yang, J.; Wei, Y.; Wang, M.; Yuan, Y.; Xu, C.; Xie, Y.; Li, X.; Zhou, S.
In the present work, we report the 25 MeV oxygen irradiation effects in n-type single crystal β-Ga2O3 at different fluences. We demonstrate that the symmetric stretching modes and bending vibrations of GaO4 and GaO6 units are impaired upon increasing O irradiation fluence. Blue and green photoluminescence emission bands are found to be mainly associated with gallium-oxygen divacancies, gallium vacancies and oxygen interstitials. The increase of optically active centers at low fluence and the photoluminescence quenching at high fluence are ascribed to the reduction of carrier density and the production of non-radiative recombination centers, respectively. The results envisage the possibility of obtaining pre-designed spectral behaviours by varying the oxygen irradiation fluence.
Keywords: β-Ga2O3, ion irradiation, photoluminescence, radiation defect

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  • Secondary publication expected from 23.08.2019

Publ.-Id: 27845 - Permalink


Coordination polymers of tetravalent neptunium with aromatic polycarboxylate ligands
Volkringer, C.ORC; Martin, N. P.ORC; März, J.; Hennig, C.ORC; Ikeda-Ohno, A.ORC; Loiseau, T.ORC
Coordination polymers are organic-inorganic complexes built up from the association of metallic centers with O- or N-donor ligands. In the particular case of actinides (An), previous literature mainly has reported the synthesis of solid networks bearing U(VI) or Th(IV). Trans-uranium elements have been much less studied due to their high radiotoxicity and limited amount of the material source.
In this work, we studied the crystallization of Np(IV) with various aromatic polycarboxylate ligands in different solvents and analyzed their crystal structures. In water, an infinite chain of Np2O2(H2O)2(1,2-bdc)2 were isolated in the presence of phthalate, whereas mellitic acid leads to the oxidation of Np(IV) to Np(V) and the formation of inorganic layers of {NpO7H2O0-2}.1 The use of other solvents allowed the crystallization of large polynuclear discrete Np(IV) clusters. For example, using DMF, the hexanuclear unit of [Np6O4(OH)4] has been obtained with different dicarboxylic ligands and is the basic building unit to form an open-framework structure (Figure 1, left). This framework revealed the isolation of the hexanuclear cluster An6O8 with Np(IV).2 The formation of the giant neptunium-based polyoxo cluster called Np38 will be also presented.
Keywords: Actinides, neptunium, tetravalent, coordination polymers, metal-organic frameworks
  • Lecture (Conference)
    International Conference on Coordination Chemistry 2018, 03.08.2018, Sendai, Japan

Publ.-Id: 27843 - Permalink


Short-Range Order in Amorphous and Crystalline Ferroelectric Hf0.5Zr0.5O2
Erenburg, S. B.; Trubina, S. V.; Kvashnina, K. O.; Kruchinin, V. N.; Gritsenko, V. V.; Chernikova, A. G.; Markeev, A. M.
The microstructures of amorphous and polycrystalline ferroelectric Hf0.5Zr0.5O2 films are studied by X-ray spectroscopy and ellipsometry. EXAFS spectra demonstrate that the amorphous film consists of an “incompletely mixed” solid solution of metallic oxides HfO2 and ZrO2. After rapid thermal annealing, the mixed Hf0.5Zr0.5O2 oxide films have a more ordered polycrystalline structure, and individual Hf and Zr monoxide islands form in the films. These islands are several nanometers in size and have a structure that is similar to the monoclinic structure of HfO2 and ZrO2. The presence of the HfO2 and ZrO2 phases in the Hf0.5Zr0.5O2
films is also detected by ellipsometry

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  • Secondary publication expected

Publ.-Id: 27841 - Permalink


When defects are not defects
Krasheninnikov, A. V.ORC
Line defects in two-dimensional borophene can self-assemble into new crystalline phases, blurring the distinctions between perfect and defective crystal.
Keywords: 2D materials, STM, defects, first-principles calculations

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  • Secondary publication expected from 23.02.2019

Publ.-Id: 27840 - Permalink


Ag nanoparticles embedded in Nd:YAG crystals irradiated with tilted beam of 200 MeV Xe ions: optical dichroism correlated to particle reshaping
Li, R.; Pang, C.; Amekura, H.; Ren, F.; Hübner, R.; Zhou, S.; Ishikawa, N.; Okubo, N.; Chen, F.
We report on the fabrication of reshaped Ag nanoparticles (NPs) embedded in a Nd:YAG crystal by combining Ag ion implantation and swift heavy Xe ion irradiation. The localized surface plasmon resonance (LSPR) effect is proved to be efficiently modulated according to the phenomenon of polarization-dependent absorption. The LSPR peak located at 448 nm shows red shift and blue shift at 0° and 90° polarization, respectively, which is in good agreement with calculation by discrete dipole approximation. Based on the near-field intensity distribution, the interaction between reshaped NPs shows a non-ignorable effect on the optical absorption. Furthermore, the polarization-dependence of the photoluminescence (PL) intensity is analyzed, which is positively related to the modulated LSPR absorption. It demonstrates the potential of the enhancement of PL intensity by embedded plasmonic Ag NPs. This work breaks the conventional view of the quenching effect of NPs by ion irradiation and opens a new way to realize the modulation of optical dichroism.
Keywords: nanoparticles, localized surface plasmon resonance, swift heavy ion irradiation, ND:YAG crystal

Publ.-Id: 27839 - Permalink


Development and validation of NTCP models for acute side-effects resulting from proton beam therapy of brain tumours
Dutz, A.; Lühr, A.; Agolli, L.; Troost, E. G. C.; Krause, M.; Baumann, M.; Vermeren, X.; Geismar, D.; Schapira, E. F.; Bussière, M.; Daly, J. E.; Bussière, M. R.; Timmermann, B.; Shih, H. A.; Löck, S.
Background: The limited availability of proton beam therapy (PBT) requires individual treatment selection strategies, such as based on normal tissue complication probability (NTCP). We developed and externally validated NTCP models for common acute side-effects following PBT in brain tumour patients in effort to provide guidance on optimising patient quality of life.
Methods: An exploration cohort including 113 adult brain tumour patients who underwent PBT was investigated for the following endpoints: alopecia, scalp erythema, headache, fatigue and nausea. Dose–volume parameters of associated normal tissues were used for logistic regression modelling.
Statistically significant parameters showing high area under the receiver operating characteristic curve (AUC) values in internal cross-validation were externally validated on two cohorts of 71 and 96 patients, respectively.
Results: Statistically significant correlations of dose–volume parameters of the skin for erythema and alopecia were found. In internal cross-validation, the following prognostic parameters were selected: V35Gy (absolute volume receiving 35 Gy) for erythema grade ≥1, D2% (dose to 2% of the volume) for alopecia grade ≥1 and D5% for alopecia grade ≥2. Validation was successful for both cohorts with AUC >0.75. A bivariable model for fatigue grade 1 could not be validated externally. No correlations of dose–volume parameters of the brain were seen for headache or nausea.
Conclusion: We developed and successfully validated NTCP models for scalp erythema and alopecia in primary brain tumour patients treated with PBT.
Keywords: NTCP models, Brain tumours, Acute side-effects, Proton beam therapy

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Publ.-Id: 27838 - Permalink


Keine Überlegenheit der Protonentherapie gegenüber der IMRT beim lokal fortgeschrittenen NSCLC
Dutz, A.; Troost, E. G. C.; Löck, S.
Hintergrund: Inoperable und lokal fortgeschrittene nicht-kleinzellige Bronchialkarzinome (NSCLC) werden standardgemäß mit einer simultanen Radiochemotherapie behandelt. In dieser Arbeit untersuchten die Autoren die Hypothese, dass die Lungentoxizität (Strahlenpneumonitis, RP) nach PSPT geringer ist, ohne die Tumorkontrolle zu gefährden.
Methodik: Gemäß Protokoll wurden 149 Patienten behandelt (IMRT: 92, PSPT: 57). Als primärer kombinierter Endpunkt der randomisierten Studie wurde das erste Auftreten einer RP vom Grad ≥3 oder das Auftreten eines Lokalrezidivs innerhalb eines Jahres betrachtet.
Resultate: Die PSPT reduzierte die mittlere Herzdosis signifikant (p = 0,002), während in der mittleren Lungen- und Ösophagusdosis keine Unterschiede zur IMRT auftraten. Eine RP vom Grad ≥3 entwickelten 12 Patienten, je 6 pro Studienarm. Lokalrezidive traten ähnlich häufig in beiden Armen auf. Damit ergab sich kein signifikanter Unterschied im primären kombinierten Endpunkt (IMRT: 17,4 %, PSPT: 21,1 %; p = 0,175). Das mediane Gesamtüberleben betrug 29,5 Monate im IMRT-Arm und 26,1 Monate im PSPT-Arm.
Schlussfolgerung der Autoren: Bei Patienten mit lokal fortgeschrittenem NSCLC konnte kein Unterschied in der Häufigkeit von RP Grad ≥3 oder dem Auftreten von Lokalrezidiven zwischen IMRT und PSPT nachgewiesen werden.
Kommentar: Die vorliegende Arbeit präsentiert die erste abgeschlossene randomisierte klinische Studie, die bei Patienten mit lokal fortgeschrittenem NSCLC prospektiv Ergebnisse von IMRT mit PSPT vergleicht. Das gewählte adaptive Bayes-Studiendesign zur Randomisierung der Patienten erhöht die ethische Vertretbarkeit randomisierter Studien. Allerdings ist der Dosisvergleich in benachbarten Risikoorganen zwischen beiden Strahlungsmodalitäten kritisch zu sehen. Im PSPT-Arm wurden mehr Patienten mit der höheren Dosis von 74 Gy bestrahlt als im IMRT-Arm. Die hohe Rate an RP im PSPT-Arm wird mit einer Lernkurve des Personals erklärt, obwohl eine andere plausible Erklärung die signifikant höheren Tumorvolumina sein können. Eine Analyse der mittleren biologischen Lungendosis könnte vorteilhafter sein als die Analyse der physikalischen Dosis.

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Publ.-Id: 27837 - Permalink


Defect-induced exchange bias in a single SrRuO3 layer
Wang, C.; Chen, C.; Chang, C.-H.; Tsai, H.-S.; Pandey, P.; Xu, C.; Böttger, R.; Chen, D.; Zeng, Y.-J.; Gao, X.; Helm, M.; Zhou, S.
Exchange bias stems from the interaction between different magnetic phases and therefore it generally occurs in magnetic multilayers. Here we present a large exchange bias in a single SrRuO3 layer induced by helium ion irradiation. When the fluence increases, the induced defects not only suppress the magnetization and the Curie temperature, but also drive a metal-insulator transition at a low temperature. In particular, a large exchange bias field up to ~ 0.36 T can be created by the irradiation. This large exchange bias is related to the coexistence of different magnetic and structural phases that are introduced by embedded defects. Our work demonstrates that spintronic properties in complex oxides can be created and enhanced by applying ion irradiation.
Keywords: Exchange bias, Magnetization, Oxide thin film, Lattice distortion, Defect engineering

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  • Secondary publication expected from 23.07.2019

Publ.-Id: 27835 - Permalink


Molecular interactions of fungi with U(VI) studied by microscopic and spectroscopic methods
Wollenberg, A.; Merroun, M.; Guenther, A.; Raff, J.; Stumpf, T.
Fungi play an important role in the microbial community of soil and their metabolic processes can influence the migration of radionuclides in the environment by different interaction processes like mainly sorption, accumulation or mineralization. The immobilization of radionuclides reduces their mobility, which thus prevents also the entry of radionuclide into the water pathway and into the food chain.
For this reasons the aim of this study is to determine the potential of fungi for precautionary radiation protection methods and bioremediation procedures for contaminated soils. In the assessment of the suitability of fungi, the first step is to investigate the molecular interactions with radionuclides in more detail to identify dominant interaction processes. Therefore, binding experiments with different initial conditions were performed and the molecular binding form was investigated with time-resolved laser-induced fluorescence spectroscopy. Furthermore, TEM-EDX analyses were used to determine whether immobilization takes place within the cell or on the cell surface.
Keywords: Fungi, Uranium, TRLFS, TEM-EDX
  • Lecture (Conference)
    Goldschmidt, 12.-17.08.2018, Boston, USA

Publ.-Id: 27828 - Permalink


Nachrechnung von Kondensationsversuchen in der COSMEA-Versuchsanlage mit dem Programm ATHLET
Zhang, Y.; Leyer, S.; Geißler, T.; Hampel, U.
Sicherheit ist ein wesentliches Thema im Entwicklungsprozess von Kernkraftwerken. Mehrere Reaktortypen der Generation III und III+ enthalten ein passives Sicherheitssystem zur Unfallkontrolle ohne externe Stromversorgung. Ein Beispiel ist der Notkondensator (EC) des KERENA-Reaktorkonzeptes. Der EC entzieht dem Reaktordruckbehälter bei Störfällen Wärme. Die Versuchsanlage COSMEA am Helmholtz Zentrum Dresden Rossendorf (HZDR) wurde eingerichtet, um die Strömungsmorphologie und die Wärmeübertragungsstruktur der Kondensation in einem leicht geneigten Rohr zu untersuchen. In diesem Beitrag werden Nachrechnung des Kondensationsprozesses in der Versuchsanlage COSMEA mit den thermohydraulischen Systemcode ATHLET vorgestellt. Die Leistungsfähigkeit der ATHLET Wärmeübertragungsmodelle wurde bestimmt. Die Simulationsergebnisse wurden mit den Experimenten verglichen. Der Wärmefluss, die Kondensationsrate und die Temperatur des Kühlwassers während der Kondensation wurden analysiert.

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  • Secondary publication expected from 01.06.2019

Publ.-Id: 27827 - Permalink


Analysis of flow patterns in a rotating packed bed using gamma-ray computed tomography
Bieberle, A.; Gross, K.; Gladyszewski, K.

In this study, gamma-ray computed tomography is employed to quantify the liquid hold-up and its distribution in a rotating packed bed using:

  • different insets
  • different rotational speeds
  • different fluid rate flows

Keywords: gas-liquid flow pattern; local liquid hold-up; rotating packed bed; fast imaging; computed tomography
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2018-08-17
    DOI: 10.14278/rodare.42

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Publ.-Id: 27826 - Permalink


Nanostructuring few-layer graphene films with swift heavy ions for electronic application: tuning of electronic and transport properties
Nebogatikova, N. A.; Antonova, I. V.; Erohin, S. V.; Kvashnin, D. G.; Olejniczak, A.; Volodin, V. A.; Skuratov, A. V.; Krasheninnikov, A. V.ORC; Sorokin, P. B.; Chernozatonskii, L. A.
he morphology and electronic properties of single and few-layer graphene films nanostructured by the impact of heavy high-energy ions have been studied. It is found that ion irradiation leads to the formation of nano-sized pores, or antidots, with sizes ranging from 20 to 60 nm, in the upper one or two layers. The sizes of the pores proved to be roughly independent of the energy of the ions, whereas the areal density of the pores increased with the ion dose. With increasing ion energy (>70 MeV), a profound reduction in the concentration of structural defects (by a factor of 2–5), relatively high mobility values of charge car- riers (700–1200 cm2 V−1 s−1) and a transport band gap of about 50 meV were observed in the nano- structured films. The experimental data were rationalized through atomistic simulations of ion impact onto few-layer graphene structures with a thickness matching the experimental samples. We showed that even a single Xe atom with energy in the experimental range produces a considerable amount of damage in the graphene lattice, whereas high dose ion irradiation allows one to propose a high probability of con- secutive impacts of several ions onto an area already amorphized by the previous ions, which increases the average radius of the pore to match the experimental results. We also found that the formation of “welded” sheets due to interlayer covalent bonds at the edges and, hence, defect-free antidot arrays is likely at high ion energies (above 70 MeV).
Keywords: graphene, ion irradiation

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  • Secondary publication expected from 03.07.2019

Publ.-Id: 27825 - Permalink


Erratum: Charged Point Defects in the Flatland: Accurate Formation Energy Calculations in Two-Dimensional Materials [Phys. Rev. X 4, 031044 (2014)]
Komsa, H.-P.; Berseneva, N.; Krasheninnikov, A. V.ORC; Nieminen, R. M.
No "expressive" abstract available.
Keywords: 2D materials, first-principles calculaitons

Publ.-Id: 27824 - Permalink


1T phase as an efficient hole injection layer to TMDs transistors: a universal approach to achieve p-type contacts
Hu, X.; Wang, Y.; Shen, X.; Krasheninnikov, A. V.ORC; Sun, L.; Chen, Z.
Recently, the fabricated MoS2 field effect transistors (FETs) with 1T-MoS2 electrodes exhibit excellent performance with rather low contact resistance, as compared with those with metals deposited directly on 2H-MoS2 (Kappera et al 2014 Nat. Mater. 13 1128), but the reason for that remains elusive. By means of density functional theory calculations, we investigated the carrier injection at the 1T/2H MoS2 interface and found that although the Schottky barrier height (SBH) values of 1T/2H MoS2 interfaces can be tuned by controlling the stacking patterns, the p-type SBH values of 1T/2H MoS2 interfaces with different stackings are lower than their corresponding n-type SBH values, which demonstrated that the metallic 1T phase can be used as an efficient hole injection layer for 2H-MoS2. In addition, as compared to the n-type Au/MoS2 and Pd/MoS2 contacts, the p-type SBH values of 1T/2H MoS2 interfaces are much lower, which stem from the efficient hole injection between 1T-MoS2 and 2H-MoS2. This can explain the low contact resistance in the MoS2 FETs with 1T-MoS2 electrodes. Notably, the SBH values can be effectively modulated by an external electric field, and a significantly low p-type SBH value can be achieved under an appropriate electric field. We also demonstrated that this approach is also valid for WS2, WSe2 and MoSe2 systems, which indicates that the method can most likely be extended to other TMDs, and thus may open new promising avenues of contact engineering in these materials.
Keywords: 2D materials, first-principles simulations

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  • Secondary publication expected from 13.06.2019

Publ.-Id: 27823 - Permalink


Fermi surface reconstruction and dimensional topology change in Nd-doped CeCoIn5
Klotz, J.; Götze, K.; Sheikin, I.; Förster, T.; Graf, D.; Park, J.-H.; Choi, E. S.; Hu, R.; Petrovic, C.; Wosnitza, J.; Green, E. L.
We performed low-temperature de Haas–van Alphen effect measurements on a Ce1−xNdxCoIn5 series, for x = 0.02, 0.05, 0.1, and 1, down to T = 40 mK using torque magnetometry in magnetic fields up to 35 T. Our results indicate that a Fermi surface (FS) reconstruction occurs from a quasi-two-dimensional topology for Nd-2% to a rather three-dimensional one for Nd-5%, thus reducing the possibility of perfect FS nesting. The FS evolves further with increasing Nd content with no observed divergence of the effective mass between Nd-2% and 10%, consistent with the crossing of a spin density wave type of quantum critical point. Our results elucidate the origin of the Q phase observed at the 5% Nd-doping level [Raymond et al., J. Phys. Soc. Jpn. 83, 013707 (2014)].

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Publ.-Id: 27822 - Permalink


Spontaneous and field-induced magnetic phase transitions in Dy2Co3Al9: Effects of exchange frustration
Gorbunov, D. I.; Henriques, M. S.; Qureshi, N.; Ouladdiaf, B.; Salazar Mejia, C.; Gronemann, J.; Andreev, A. V.; Petricek, V.; Green, E. L.; Wosnitza, J.
Due to the long-range oscillatory character of RKKY exchange interactions, for Dy2Co3Al9 there exist positive and negative couplings between theDymagnetic moments that lead to magnetic frustration. As a result, the ground state can be easily perturbed, and the system displays a number of spontaneous and field-induced phase transitions. We performed magnetization, magnetic-susceptibility, specific-heat, and electrical-resistivity measurements as well as neutron-diffraction experiments on a single crystal. We find two transitions to distinct incommensurate antiferromagnetic phases at 6.2 and 5.2 K that evolve to a commensurate phase at 3.7 K. In applied magnetic field, new phases emerge. Field-dependent magnetization exhibits a multistep metamagnetic process with sharp transitions accompanied by pronounced magnetoresistance changes. The large number of phases and their complex magnetic structures suggest that the physical properties of Dy2Co3Al9 are ruled by exchange frustration in the presence of a large magnetocrystalline anisotropy.

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Publ.-Id: 27821 - Permalink


Experimental investigations and rate-based modeling of CO₂ absorption with sandwich packings
Flechsig, S.; Sohr, J.; Schubert, M.; Hampel, U.; Kenig, E. Y.
In the process industry, packed columns are used in a variety of fluid separation operations, e.g. in distillation and absorption, in order to create a desirable flow pattern of two-phase systems. Due to the high energy requirements of separation processes, the interest on their optimization is vital. In particular, column internals have permanently been the focus of investigations.
An improvement of the separation efficiency can be achieved by the application of sandwich packings. The latter consist of two alternating layers of industrially available standard packings with different specific surface areas, one with lower (the so-called holdup layer) and another with higher (the so-called de-entrainment layer) capacity. Sandwich packings are typically used at operating conditions between the flooding points of holdup layer and de-entrainment layer. Above the holdup layer, a froth sublayer is formed, which reveals high separation efficiency due to intensified phase mixing. In the upper section of the de-entrainment layer, film-like flow patterns can be observed [1]. Under certain conditions, this intensive heterogeneous flow pattern can be used in a beneficial way for fluid separation processes. However, the application of this integrated packing type is hindered by lacking validated design methods [2].
An accurate prediction of the performance characteristics is essential for the design of sandwich packings. In our project, the effects of the individual flow regimes on fluid dynamics and mass transfer are investigated complementarily with both experimental and theoretical studies. In order to determine the impact of each individual flow regime, experiments on an absorption/desorption plant are supplemented by flow imaging measurements of sandwich packings. At the Paderborn University, CO2 absorption is examined in a pilot plant for various design and operating parameters. This plant allows measuring temperature profiles of the gas phase as well as concentration profiles of both phases. At the Helmholtz-Zentrum Dresden-Rosendorf, a detailed view on the phase distribution within the sandwich packings is realized bymeans of an ultrafast X-ray tomography. The measured data from both experimental methods are used to establish correlations for mass transfer coefficients, interfacial area, holdup and pressure drop, which are applied in a rate-based stage model for CO2 absorption processes with aqueous amine solutions.
The absorption experiments were performed under ambient conditions in a column with an inner diameter of 0,1 m and 3,2 m packing height. The influence of different operating and design parameters on the separation characteristics in sandwich packings was studied in order to identify appropriate operating conditions and to provide a sufficient basis for the experimental validation of a model, which is able to describe the heterogeneous flow patterns. In particular, we investigated the impact of the holdup-layer height and its corresponding specific surface area. In addition, the inclination angle of the flow channels in the de-entrainment layer was varied.
The rate-based approach, which accounts for the specifics of different column internals via correlations, was applied. We expected that different fluid dynamic regimes would have different impacts on the mass transfer. Therefore, each fluid dynamic regime was considered individually. The column was represented as a sequence of alternating segments, and each segment was described by a corresponding set of correlations. Experimental data of the CO2 absorption with sandwich packings were then compared with simulation results.
Acknowledgments
The authors are grateful to the Deutsche Forschungsgemeinschaft (DFG) for financial support (KE 837/26-1, HA 3088/10-1).
References
[1] U. Brinkmann, B. Kaibel, M. Jödecke, J. Mackowiak, E.Y. Kenig: Beschreibung der Fluiddynamik von Anstaupackungen, Chemie Ingenieur Technik 84, 36-45 (2012).
[2] Ö. Yildirim, E.Y. Kenig: Rate-based modelling and simulation of distillation columns with sandwich packings, Chemical Engineering and Processing: Process Intensification 98, 147-154 (2015).
  • Lecture (Conference)
    ACHEMA Congress 2018, 11.-15.06.2018, Frankfurt am Main, Deutschland

Publ.-Id: 27815 - Permalink


Messung des 478 keV Gammaproduktionsquerschnitts nach inelastischer Streuung an ⁷ Li
Frotscher, A.
The inelastic neutron cross section of 7Li has no sharp resonances and a fairly low threshold of 546 keV. Below the breakup threshold at 5291 keV only one gamma-ray is emitted at E = 477,6 keV. It is therefore suited as a reference cross section. Lithium has technical usage as a 3H-producer in future fusion reactors as well as in molten salt reactors. But there are recent measurements disagreeing with already evaluated data. To resolve this dissonance, an 170 h Experiment was carried out at the nELBE facility of the HZDR. A 4 mm thick LiF-disk was used as a target, the neutron flux was determined with a 235U parallel plate fission chamber. The flight path for the 7Li(n,n’ )7Li reaction was 8,3 m. As detectors four two-inch LaBr3-detectors as well as three three-inch LaBr3-detectors and two miniball-type HPGe detectors with three 60 % crystals each were used. The measurement of the cross section is solely a measurement of the de-excitation of the first exited 7Li-State at 477,6 keV. The second exited state at 4,63 MeV already decays via particle emission and thus does not contribute any gamma-radiation. The experiment benefits from the high neutron flux at nELBE (80 n/s/keV @ 1 MeV) as well as from the precise fission chamber of the PTB (H19) for the neutron flux calibration. A Geant4-Simulation is used to determine correction factors as the transmission from the H19 to the target as well as the multiple scattering correction and the self absorption of the 477,6 keV Gamma-Rays. The deduced cross section from both detector types are consistent, but they can’t reproduce the data from Nyman et al. The deviations are up to 20 %. The half life of the by means of bremsstrahlung in air produced positroniums in the experiment is 116(7) ns.
Keywords: nELBE, inelastic neutron scattering, fast neutrons, Li-7
  • Master thesis
    TU Dresden, 2017
    Mentor: Dr. Arnd Junghans

Publ.-Id: 27814 - Permalink


Fano signatures between intersubband and ponderomotive responses in MQW structures
Pedroso, D. D. M.; Schmidt, J.; Passaro, A.; Helm, M.; Schneider, H.
We present an in-depth theoretical and numerical discussion on the Fano signatures observed in differential transmission spectra obtained from multiquantum well structures. These signatures stem from ponderomotive and intersubband polarization currents modified by the coupling between the optical responses of different layers. A detailed discussion of this process is provided, evaluating quantitatively the amplitude and shape of the Fano signatures and their dependence on structural parameters, such as carrier concentration and layer width. The theoretical model described here aims to predict quantitatively the weight of the contributions of the ponderomotive currents in relation to the intersubband ones. In order to include the effect of the entire structure in the theoretical spectra, the optical response of each layer is addressed within the density matrix formalism and encompassed in an optical transfer matrix. This method also ensures the correct inclusion of the phase sensitive superposition of optical responses of different layers on which the Fano signatures are based. Numerical simulations obtained from the presented theoretical approach are in excellent agreement with the behaviour observed in previous experiments.
Keywords: Fano interference, intersubband transition, free-carrier absorption, GaAs, multiple quantum well, MQW

Publ.-Id: 27811 - Permalink


Quantitative predictions of LWFA simulation with PIConGPU - from improved modeling to new measurement methods via synthetic radiation diagnostics
Pausch, R.; Debus, A.; Schramm, U.; Bussmann, M.; Steiniger, K.; Widera, R.; Huebl, A.; Garten, M.; Irman, A.; Couperus, J.; Zarini, O.; Köhler, A.
In a close interplay between particle-in-cell simulations and experimental measurements, we present new insights into the modeling of laser wakefield accelerators and discuss the arising challenges for laboratory diagnostics. These challenges were tackled by developing new methods for determining key parameters of the experiment by studying synthetic radiation diagnostics predicted by simulations.

The combination of an unprecedented experimental campaign studying the parameter dependence of beam loading during LWFA and an accompanying, extensive simulation campaign using the 3D3V particle-in-cell code PIConGPU made it possible to provide unique feedback between experiment and theory. This poster shows the step-by-step improvements through this interplay from the simulation perspective. Quantitatively more accurate methods such as the use of Gauss-Laguerre modes or a variety of ionization models are presented as well as more performant computationally procedures. Only through these improvements could the dynamics occurring in the experiment be reproduced and a deeper insight into the self-truncated ionization injection method be gained.

Moreover, this interplay also revealed the limits of current laboratory diagnostics. Synthetic in-situ radiation diagnostics in PIConGPU instigated the development of new diagnostic methods for experiments. For example, the shift of the laser focus position, compared to the vacuum, due to self-focusing in the plasma can now be quantified by spectral radiation signatures. Applying these new methods will enable an even more accurate understanding of laser plasma dynamics in experiments in the near future.
Keywords: Radiation, LWFA, aprticle-in-cell, PIConGPU
  • Poster
    The fourth annual meeting of the programme "Matter and Technologies", 12.-14.06.2018, Berlin, Deutschland
  • Lecture (Conference)
    The fourth annual meeting of the programme "Matter and Technologies", 12.-14.06.2018, Berlin, Deutschland

Publ.-Id: 27809 - Permalink


Three-Dimensional Composition and Electric Potential Mapping of III−V Core−Multishell Nanowires by Correlative STEM and Holographic Tomography
Wolf, D.; Hübner, R.; Niermann, T.; Sturm, S.; Prete, P.; Lovergine, N.; Büchner, B.; Lubk, A.
The nondestructive characterization of nanoscale devices, such as those based on semiconductor nanowires, in terms of functional potentials is crucial for correlating device properties with their morphological/materials features, as well as for precisely tuning and optimizing their growth process. Electron holographic tomography (EHT) has been used in the past to reconstruct the total potential distribution in three dimension but hitherto lacked a quantitative approach to separate potential variations due to chemical composition changes (mean inner potential, MIP) and space charges. In this letter, we combine and correlate EHT and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) tomography on an individual ⟨111⟩ oriented GaAs-AlGaAs core-multishell nanowire (NW). We obtain excellent agreement between both methods in terms of the determined Al concentration within the AlGaAs shell, as well as thickness variations of the few nanometer thin GaAs shell acting as quantum well tube. Subtracting the MIP determined from the STEM tomogram enables us to observe functional potentials at the NW surfaces and at the Au-NW interface, both ascribed to surface/interface pinning of the semiconductor Fermi level.
Keywords: GaAs-AlGaAs, III−V nanowire, 3D elemental mapping, functional potential, quantum well tube, tomography, holography

Publ.-Id: 27807 - Permalink


Terahertz pump-induced anisotropy and nonlinear susceptibility in graphene
Schneider, H.; König-Otto, J. C.; Mittendorff, M.; Winzer, T.; Kadi, F.; Malic, E.; Knorr, A.; Wang, Y.; Belyanin, A.; Pashkin, A.; Helm, M.; Winnerl, S.
We report on investigations of the carrier dynamics in graphene close to the Dirac point by nonlinear terahertz spectroscopy. At terahertz frequencies and low temperatures, optical-phonon scattering is suppressed. In this case, the decay of the pump-induced anisotropy in the carrier distribution is observed to be very slow, long as several ps, which is theoretically explained by non-collinear Coulomb scattering. In Landau-quantized graphene, degenerate four-wave mixing experiments in resonance to the lowest Landau level transition allow us to investigate the induced coherent polarization and to compare its dependence on THz field strength and B-field detuning with theoretical expectations.
Keywords: graphene, nonlinear terahertz spectroscopy, nonlinear susceptibility, pump-probe
  • Poster
    34-th International Conference on the Physics of Semiconductors (ICPS 2018), 29.07.-03.08.2018, Montpellier, Frankreich

Publ.-Id: 27805 - Permalink


High-performance and room-temperature QWIPs & terahertz spectroscopy
Schneider, H.
The topic of this seminar talk is high-performance and room-temperature quantum well photodetectors and terahertz spectroscopy.
Keywords: quantum well infrared photodetector, terahertz spectroscopy
  • Lecture (others)
    Seminarvortrag, Yunnan University, 03.05.2018, Kunming, China

Publ.-Id: 27804 - Permalink


Nonlinear THz spectroscopy of graphene and GaAs quantum wells using a free-electron laser
Schneider, H.
This talk reviews some recent experiments using FEL-based intense narrow-band terahertz fields, in particular pump-induced optical anisotropy and nonlinear four-wave mixing in graphene, and dressing of excitons, exciton-polaritons, and intersubband transitions in GaAs quantum wells.
Keywords: nonlinear terahertz spectroscopy, graphene, interaubband, exciton
  • Invited lecture (Conferences)
    The 9th International Symposium on Ultrafast Phenomena and Terahertz Waves (ISUPTW 2018), 23.-26.04.2018, Changsha, China
  • Invited lecture (Conferences)
    International Conference on "Synchrotron and Free electron laser Radiation: generation and application" (SFR-2018), Budker Institute of Nuclear Physics, 25.-28.06.2018, Novosibirsk, Russische Föderation

Publ.-Id: 27803 - Permalink


Nonlinear THz free-electron laser spectroscopy of graphene and GaAs quantum wells
Schneider, H.
This talk reviews some recent experiments on graphene and on GaAs quantum wells using FEL-based strong THz fields.
In graphene, we have investigated the pump-induced anisotropy of the carrier distribution upon excitation with linearly polarized light. Since optical-phonon scattering is suppressed at THz frequencies and low temperatures, we observe the decay of this anisotropy to be very slow, as long as several ps, which is theoretically explained by non-collinear Coulomb scattering. We also report on degenerate four-wave mixing experiments in Landau-quantized graphene to investigate the induced coherent polarization. In GaAs quantum wells, intense narrow-band THz fields are exploited for dressing elementary electronic excitations. We will address THz-induced dressing of excitons, exciton-polaritons, and intersubband transitions.
Keywords: Graphene, intersubband, nonlinear terahertz spectroscopy,
  • Lecture (others)
    Seminarvortrag, University of California at Santa Barbara (UCSB), 05.02.2018, Santa Barbara, USA
  • Lecture (others)
    Physikalisches Kolloquium der TU Chemnitz, 13.06.2018, Chemnitz, Deutschland
  • Lecture (others)
    Seminar, Chengdu Campus of CAEP, 23.07.2018, Chengdu, China

Publ.-Id: 27802 - Permalink


Terahertz orientational relaxation and phase relaxation in graphene
Schneider, H.; König-Otto, J. C.; Mittendorff, M.; Winzer, T.; Kadi, F.; Malic, E.; Knorr, A.; Wang, Y.; Belyanin, A.; Pashkin, A.; Helm, M.; Winnerl, S.
We report on investigations of the carrier dynamics in graphene close to the Dirac point by nonlinear terahertz spectroscopy. At terahertz frequencies and low temperatures, optical-phonon scattering is suppressed. In this case, the decay of the pump-induced anisotropy in the carrier distribution is observed to be very slow, long as several ps, which is theoretically explained by non-collinear Coulomb scattering. In Landau-quantized graphene, degenerate four-wave mixing experiments in resonance to the lowest Landau level transition allow us to investigate the induced coherent polarization and to compare its dependence on THz field strength and B-field detuning with theoretical expectations.
Keywords: graphene, nonlinear terahertz spectroscopy, nonlinear susceptibility, four-wave mixing, pump-probe
  • Lecture (Conference)
    SPIE Photonics West, Symposium on "Ultrafast Phenomena and Nanophotonics XXII", 27.01.-01.02.2018, San Francisco, USA

Publ.-Id: 27801 - Permalink


Halbleitertechnik im Osten der Republik
Skorupa, W.
Eingeladener Vortrag anlässlich des Workshops zum 60. Gründungsjubiläum des Institutes für Halbleitertechnik an der Universität Stuttgart mit Bezug zur Ionenstrahlphysik und -technologie am Forschungsstandort Dresden-Rossendorf, jetzt Helmholtzzentrum Dresden-Rossendorf
Keywords: Halbleitertechnik, Chiptechnologie, DDR, Geschichte, Ionenstrahlphysik, Ionenstrahltechnologie
  • Invited lecture (Conferences)
    Workshop anlässlich des 60. Jahrestages des Institutes für Halbleitertechnik an der Universität Stuttgart, 01.08.2018, Stuttgart, Deutschland

Publ.-Id: 27800 - Permalink


All-optical quantum thermometry based on spin-level cross-relaxation and multicenter entanglement under ambient conditions in SiC
Anisimov, A. N.; Soltamov, V. A.; Breev, I. D.; Babunts, R. A.; Mokhov, E. N.; Astakhov, G. V.; Dyakonov, V.; Yakovlev, D. R.; Suter, D.; Baranov, P. G.
All-optical thermometry technique based on the energy level cross-relaxation in atomic-scale spin centers in SiC is demonstrated. This technique exploits a giant thermal shift of the zero-field splitting for centers in the triplet ground state, S=1, undetected by photoluminescence (so called “dark” centers) coupling to neighbour- ing spin-3/2 centers which can be optically polarized and read out (“bright” centers), and does not require radiofrequency fields. EPR was used to identify defects. The width of the cross-relaxation line is almost an order of magnitude smaller than the width of the excited state level-anticrossing line, which was used in all-optical ther- mometry and which can not be significantly reduced since determined by the lifetime of the excited state. With approximately the same temperature shift and the same sig- nal intensities as for excited state level-anticrossing, cross-relaxation signal makes it possible to increase the sensitivity of the temperature measurement by more than an order of magnitude. Temperature sensitivity is estimated to be approximately 10 mK/Hz1/2 within a volume about 1 μ3, allocated by focused laser excitation in a scanning confocal microscope. Using cross-relaxation in the ground states of “bright” spin-3/2 centers and “dark” S=1 centers for temperature sensing and ground state level anti-crossing of “bright” spin-3/2 centers an integrated magnetic field and tempera- ture sensor with submicron space resolution can be implemented using the same spin system. The coupling of individually addressable “bright” spin-3/2 centers connected by a chain of “dark” S=1 spins, could be considered in quantum information pro- cessing and multicenter entanglement under ambient conditions.
Keywords: Defects, Quantum Technology, Thermometry, Silicon Carbide

Publ.-Id: 27798 - Permalink


Detailed study of the Fermi surfaces of the type-II Dirac semimetallic candidates XTe2 (X = Pd, Pt)
Zheng, W.; Schönemann, R.; Aryal, N.; Zhou, Q.; Rhodes, D.; Chiu, Y.-C.; Chen, K.-W.; Kampert, E.; Förster, T.; Martin, T. M.; Mccandless, G. T.; Chan, J. Y.; Manousaki, E.; Balicas, L.
We present a detailed quantum oscillatory study on the Dirac type-II semimetallic candidates PdTe2 and PtTe2 via the temperature and the angular dependence of the de Haas–van Alphen and Shubnikov–de Haas effects. In high-quality single crystals of both compounds, i.e., displaying carrier mobilities between 103 and 104 cm2/ Vs, we observed a large nonsaturating magnetoresistivity which in PtTe2 at a temperature T = 1.3 K leads to an increase in the resistivity up to (5×104)% under a magnetic field μ0H = 62 T. These high mobilities correlate with their light effective masses in the range of 0.04 to 1 bare electron mass according to our measurements. For PdTe2 the experimentally determined Fermi surface cross-sectional areas show excellent agreement with those resulting from band structure calculations. Surprisingly, this is not the case for PtTe2, whose agreement between calculations and experiments is relatively poor even when electronic correlations are included in the calculations. Therefore, our study provides strong support for the existence of a Dirac type-II node in PdTe2 and probably also for PtTe2. Band structure calculations indicate that the topologically nontrivial bands of PtTe2 do not cross the Fermi level ɛF. In contrast, for PdTe2 the Dirac type-II cone does intersect ɛF, although our calculations also indicate that the associated cyclotron orbit on the Fermi surface is located in a distinct kz plane with respect to that of the Dirac type-II node. Therefore, it should yield a trivial Berry phase.

Publ.-Id: 27795 - Permalink


Experimental evidence for the microscopic mechanism of the unusual spin-induced electric polarization in GdMn2O5
Yahia, G.; Damay, F.; Chattopadhyay, S.; Baledent, V.; Peng, W.; Kim, S. W.; Greenblatt, M.; Lepetit, M.-B.; Foury-Leylekian, P.
We report in this paper the temperature evolution of the magnetic structure of GdMn2O5, in the range 2–40 K, studied by neutron diffraction on an isotope-enriched powder. We detail a thorough analysis of the microscopic mechanisms needed to release the different magnetic frustrations that are at the origin of the polarization. In addition to the usual exchange-striction term, known to be at the origin of the polarization in this family, an additional exchange-striction effect between the Gd3+ and Mn3+ spins is found to be responsible for the very large polarization in the Gd compound.

Publ.-Id: 27794 - Permalink


Pressure-induced commensurate order in TbMn2O5 and DyMn2O5: Influence of rare-earth anisotropy and 3d-4 f exchange
Deutsch, M.; Peng, W.; Foury-Leylekian, P.; Baledent, V.; Chattopadhyay, S.; Fernandez-Diaz, M. T.; Hansen, T. C.; Forget, A.; Colson, D.; Greenblatt, M.; Lepetit, M.-B.; Petit, S.; Mirebeau, I.
The magnetic structure of TbMn2O5 and DyMn2O5 multiferroics has been studied by high-pressure neutron diffraction in a large pressure range up to 6.6 GPa. In both cases, we observe a pressure-induced commensurate magnetic phase with propagation vector ( 1/2 0 1/2 ), growing with pressure at the expense of the ambient pressure phases. Being previously observed in YMn2O5 and PrMn2O5, this phase is most likely a generic feature of the RMn2O5 multiferroic family. A simple model is proposed to explain qualitatively the emergence of this pressure-induced phase. Differences between TbMn2O5 and DyMn2O5 behaviors at ambient and low pressures provide clues on the interaction scheme.

Publ.-Id: 27793 - Permalink


Probing the Jeff = 0 ground state and the Van Vleck paramagnetism of the Ir5+ ions in layered Sr2Co0.5Ir0.5O4
Agrestini, S.; Kuo, C.-Y.; Chen, K.; Utsumi, Y.; Mikhailova, D.; Rogalev, A.; Wilhelm, F.; Förster, T.; Matsumoto, A.; Takayama, T.; Takagi, H.; Haverkort, M. W.; Hu, Z.; Tjeng, L. H.
We report a combined experimental and theoretical x-ray magnetic circular dichroism (XMCD) spectroscopy study at the Ir-L2,3 edges on the Ir5+ ions of the layered hybrid solid state oxide Sr2Co0.5Ir0.5O4 with the K2NiF4 structure. From theoretical simulation of the experimental Ir-L2,3 XMCD spectrum, we found a deviation from a pure Jeff = 0 ground state with an anisotropic orbital-to-spin moment ratio (Lx/2Sx = 0.43 and Lz/2S = 0.78). This deviation is mainly due to multiplet interactions being not small compared to the cubic crystal field and due to the presence of a large tetragonal crystal field associated with the crystal structure. Nevertheless, our calculations show that the energy gap between the singlet ground state and the triplet excited state is still large and that the magnetic properties of the Ir5+ ions can be well described in terms of singlet Van Vleck paramagnetism.

Publ.-Id: 27792 - Permalink


Short-range quasistatic order and critical spin correlations in α-Ru1−xIrxCl3
Do, S.-H.; Lee, W.-J.; Lee, S.; Choi, Y. S.; Lee, K.-J.; Gorbunov, D. I.; Wosnitza, J.; Suh, B. J.; Choi, K.-Y.
The magnetic ground states of the diluted α-Ru1−x IrxCl3 are systematically investigated by magnetization, specific heat, and muon spin rotation measurements. Introduction of moderate spin vacancies leads to a destabilization of the zigzag antiferromagnetic order towards a short-range ordered state. It is remarkable that the x = 0.2 sample located near a quantum critical point shows an extremely short correlation length of the magnitude of magnetic moments ζmag ∼ 1.2a (a = lattice spacing) and a power-law behavior of the magnetic susceptibility χ(T ) ∼ T−p below 14 K for μ0HIIab and below 30 K for μ0HIIc. Our work demonstrates that the α-Ru1−x IrxCl3 system hosts a short-range, quasistatic order characterized by critical spin correlations.

Publ.-Id: 27790 - Permalink


The electronic structure and band interface of cesium bismuth iodide on a titania heterostructure using hard X-ray spectroscopy
Phuyal, D.; Jain, S. M.; Philippe, B.; Johansson, M. B.; Pazoki, M.; Kullgren, J.; Kvashnina, K. O.; Klintenberg, M.; Johansson, E. M. J.; Butorin, S. M.; Karis, O.; Rensmo, H.
Bismuth halide compounds as a non-toxic alternative are increasingly investigated because of their potential in optoelectronic devices and their rich structural chemistry. Hard X-ray spectroscopy was applied to the ternary bismuth halide Cs3Bi2I9 and its related precursors BiI3 and CsI to understand its electronic structure at an atomic level. We specifically investigated the core levels and valence band using X-ray photoemission spectroscopy (PES), high-resolution X-ray absorption (HERFD-XAS), and resonant inelastic X-ray scattering (RIXS) to get insight into the chemistry and the band edge properties of the two bismuth compounds. Using these element specific X-ray techniques, our experimental electronic structures show that the primary differences between the two bismuth samples are the position of the iodine states in the valence and conduction bands and the degree of hybridization with bismuth lone pair (6s2) states. The crystal structure of the two layered quasiperovskite compounds plays a minor role in modifying the overall electronic structure, with variations in bismuth lone pair states and iodine band edge states. Density Functional Theory (DFT) calculations are used to compare with experimental data. The results demonstrate the effectiveness of hard X-ray spectroscopies to identify element specific bulk electronic structures and their use in optoelectronic devices

Publ.-Id: 27782 - Permalink


Entwicklung und Synthese neuartiger fluorhaltiger Liganden zur molekularen Bildgebung des Adenosin A2B-Rezeptors im Gehirn mittels Positronen-Emissions-Tomographie
Lindemann, M.ORC
Der G-Protein-gekoppelte A2B-Rezeptor unterscheidet sich von den anderen Adenosinrezeptorsubtypen (A1, A2A, A3) durch die niedrige Affinität zu seinem endogenen Liganden Adenosin. Es wird beschrieben, dass der Rezeptor in verschiedenen pathologischen Prozessen, die durch eine erhöhte Adenosinkonzentration ausgezeichnet sind, wie beispielsweise bei Entzündungen (Inflammation), Hypoxie oder auch Krebs, eine wichtige Rolle spielt. Ziel dieser Arbeit ist die Entwicklung eines Fluor-18 markierten Radioliganden für die molekulare Bildgebung des A2B-Rezeptors im Organismus bzw. im speziellen des Gehirns mittels PET. Es soll damit der Einfluss des Rezeptors bei neurodegenerativen, neuroinflammatorischen und neuroonkologischen Erkrankungen untersucht werden. Die hier erstellte Arbeit basiert auf drei verschiedenen Leitstrukturen: den Pyrazinen (PA), Pyrimidinen (PYM) und Xanthinen (PXS). Für die ersten beiden Strukturklassen wurden zunächst die Leitverbindung und verschiedene fluorierte Derivate dargestellt. Für die Xanthine wurden zwei verschiedene Derivate synthetisiert. Alle Verbindungen wurden hinsichtlich ihrer Affinität und Selektivität gegenüber den Adenosinrezeptorsubtypen untersucht. Für die Klasse der Pyrazine wurde die bis dahin beste Verbindung PA51 ausgewählt. Trotz geringer Defizite gegenüber der Selektivität zu den anderen Adenosinrezeptorsubtypen, sollte PA51 zur Untersuchung der Hirngängigkeit der Verbindungsklasse genutzt werden. Nach erfolgreicher manueller Radiomarkierung und Transfer in eine automatisierte Radiosynthese, wurde die In-vivo-Gehirnaufnahme (Autoradiographie, PET) und der In-vivo-Metabolismus von [18F]PA51 in Mäusen untersucht. Bei In-vivo- Verteilungsstudien in Mäusen wurde eine homogene Verteilung des Radiotracers im Gehirn bestimmt. Des Weiteren wurden Gehirn- und Plasmaproben zu unterschiedlichen Zeitpunkten mit verschiedenen Methoden (RP-HPLC und MLC) auf enthaltene Radiometabolite untersucht. Nach 30 min p.i. konnten 70% an intaktem Radiotracer und ein Hauptradiometabolit mit einem Anteil von 30% im Gehirn nachgewiesen werden. Dessen Struktur konnte durch Synthese einer nichtradioaktiven Vergleichssubstanz aufgeklärt werden. Auf Grund dieser Ergebnisse ist die Substanzklasse der Pyrazine nicht geeignet als PET Radiotracer. Im Vergleich zu den Pyrazinen sind die Pyrimidinderivate in der Literatur als metabolisch stabiler beschrieben. Aus diesem Grund wurde zunächst die Leitverbindung PYM80, unter leichter Modifizierung der beschriebenen siebenstufigen Syntheseroute, dargestellt. Die fluorierte Verbindung PYM81 wurde über eine neu entwickelte sechsstufige Syntheseroute dargestellt. Diese weist eine hohe Affinität und Selektivität zum A2B-Rezeptor auf, weshalb PYM81 großes Potential für die Anwendung als neuartiger fluorierter Radioligand für die molekulare Darstellung des A2B-Rezeptors mittels PET besitzt. Als dritte Strukturklasse wurden zwei Xanthinderivate PXS7-1 und PXS7-2 dargestellt. Diese Strukturen basieren auf dem literaturbekannten, hochaffinen und selektiven Liganden PSB-603. Durch Reduzierung des sterisch anspruchsvollen Sulfonamidrestes sollten die molare Masse und die stark polaren Eigenschaften dieser Verbindungsklasse gesenkt werden. An Stelle der sterisch anspruchsvollen Sulfonamidreste sollten kleine Substituenten wie 4-Fluorpiperidin oder 4-Amino-2-fluorpyridin eingeführt werden. Diese beiden Verbindungen zeigten moderate Affinitäten und Selektivitäten gegenüber dem A2B-Rezeptor, weshalb weitere strukturelle Modifizierungen, zur Steigerung der Affinität und Selektivität zum A2B-Rezeptor, folgen sollen.

The G protein-coupled A2B receptor differs from other adenosine receptor subtypes (A1, A2A, A3) by its low affinity towards the endogenous ligand adenosine. It is suggested to be involved in various pathological processes accompanied by increased levels of adenosine, e.g. inflammation, hypoxia, and cancer. In this work, the development and synthesis of a fluorine-18 labelled radioligand with the particular aim for the imaging of the A2B receptor is described, to enable the investigation of the function and expression of A2B receptor in the organism and the influence of neurodegenerative, neuroinflammatory and neurooncological processes with PET. This work is based on three different lead structures: pyrazines (PA), pyrimidines (PYM), and xanthines (PXS). For the first two structure classes, the syntheses of the lead and different fluorinated compounds were performed. For the xanthines two different molecules were synthesized. The binding affinities for the different adenosine receptor subtypes were determined for each compound. To check the brain penetration of the pyrazine class, the best candidate so far, PA51 (although lacking selectivity), was labeled with 18-fluorine. After transfer of the manual radiolabeling procedure to the automated synthesis module, the in vivo brain uptake and the in vivo metabolism studies of [18F]PA51 in mice were performed. The in vivo brain uptake studies (brain sampling, autoradiography and PET) showed a homogeneous distribution of [18F]PA51. After different time intervals, brain and plasma samples were investigated by using different methods for metabolite analytics, showing only 70% of intact radiotracer in the brain 30 min p.i. A main brain radiometabolite with an amount of 30% after 30 min p.i. was structurally identified by use of a synthesized nonradioactive reference compound. In summary, this compound class is not suitable for the use as PET radiotracer, because of the fast metabolism of the compound and the formation of a brain-penetrable radiometabolite. The pyrimidine derivatives are described in literature as more metabolically stable as the pyrazines. For this compound class, the lead compound PYM80 was synthesized in a slightly modified seven-step synthesic route. A fluorinated derivative, PYM81, was synthesized over a newly developed six-step synthesic route. The compound showed good affinity and selectivity towards the A2B receptor. Therefor PYM81 has a high potential as a novel fluorinated radioligand for the molecular imaging of the A2B receptor with PET. As third class, xanthine derivatives were synthesized because of the highly affine and selective lead compound PSB-603. Due to the high molar mass and high polarity of these compounds the sulfonamide group was modified. Instead of this group, a small 4-amino-2-fluoropyridine or 4-fluoropiperidine groups was introduced to form derivatives PXS7-1 and PXS7-2. The compounds showed moderate affinities and selectivities for the A2B receptor. In conclusion, various fluorinated compounds were synthesized and showed different affinities and selectivities for the A2B receptor and its subtypes. Furthermore, the synthesis of additional fluorinated structures with the pyrimidine lead structure is required to enhance affinity and selectivity. For a first checkup of the brain uptake of this compound class, PYM81 needs to be radiolabeled with fluorine-18 because of the literature described higher metabolic stability in comparison to the pyrazine derivatives. PYM81 and the class of pyrimidines had a high potential as novel ligands for imaging the A2B receptor with PET in the brain.
Keywords: A2B-Rezeptor, 18-Fluor, Pyrazine, Pyrimidine, Xanthine, Pyrido[2,3-d]pyrimidin-2,4(1H,3H)dione, Positronen-Emissions-Tomographie
  • Doctoral thesis
    Universität Leipzig, 2018
    Mentor: Prof. Dr. P. Brust, Dr. B. Wenzel
    274 Seiten

Publ.-Id: 27776 - Permalink


Structural Properties of Al–O Monolayers in SiO₂ on Silicon and the Maximization of their Negative Fixed Charge Density
Hiller, D.; Göttlicher, J.; Steininger, R.; Huthwelker, T.; Julin, J.ORC; Munnik, F.; Wahl, M.; Bock, W.; Schoenaers, B.; Stesmans, A.; König, D.
Al₂O₃ on Si is known to form an ultra-thin interfacial SiO₂ during deposition and subsequent annealing, which creates a negative fixed charge (Qfᵢₓ) that enables field-effect passivation and low surface recombination velocities in Si solar cells. Various concepts were suggested to explain the origin of this negative Qfᵢₓ. In this study we investigate Al–O monolayers (MLs) from atomic layer deposition (ALD) sandwiched between deliberately grown/deposited SiO₂ films. We show that the Al-atoms have an ultra-low diffusion coefficient (~4×10⁻¹⁸ cm²/s at 1000°C), are deposited at a constant rate of ~5×10¹⁴ Al-atoms/cm²/cycle from the first ALD-cycle on, and are tetrahedral O-coordinated, since the adjacent SiO₂ imprints its tetrahedral near-order and bond length into the Al–O MLs. By variation of the tunnel-SiO₂ thickness and the number of Al–O MLs, we demonstrate that the tetrahedral coordination alone is not sufficient for the formation of Qfᵢₓ but that a SiO₂ /Al₂O₃ interface within a tunneling distance from the substrate must be present. The Al-induced acceptor states at these interfaces have energy levels slightly below the Si valence band edge and require charging by electrons from either the Si substrate or from Si/SiO₂ dangling bonds to create the negative Qfᵢₓ. Hence, tunneling imposes limitations for the SiO₂ and Al₂O₃ layer thicknesses. In addition, Coulomb repulsion between the charged acceptor states results in an optimum number of Al–O MLs, i.e., separation of both interfaces. We achieve maximum negative Qfᵢₓ of ~5×10¹² cm⁻² (comparable to thick ALD-Al₂O₃ on Si) with ~1.7 nm tunnel-SiO₂ and just 7 ALD-Al₂O₃ cycles (~8 Å) after optimized annealing at 850°C for 30 s. The findings are discussed in the context of a passivating, hole-selective tunnel contact for high-efficiency Si solar cells.
Keywords: atomic layer deposition, aluminum oxide, silicon oxide, negative fixed charge, silicon surface passivation, hole-selective contact

Publ.-Id: 27775 - Permalink


Modification of magnetic properties of Pt/Co/Pt Films by Ga+ Ion irradiation: Focused versus uniform irradiation
Sveklo, I.; Mazalski, P.; Jaworowicz, J.; Jamet, J.-P.; Vernier, N.; Mougin, A.; Ferre, J.; Kisielewski, M.; Zablotskii, V.; Bourhis, E.; Gierak, J.; Postava, K.; Fassbender, J.; Kanak, J.; Maziewski, A.
30 keV Ga+ irradiation-induced changes of magnetic and magneto-optical properties of sputtered Pt/Co/Pt ultrathin trilayers films have been studied as a function of the ion fluence. Out-of-plane magnetic anisotropy states with enhanced magneto-optical e ects were evidenced for specific values of cobalt thickness and irradiation fluence. Results obtained after uniform or quasi-uniform focused ion beam irradiation on either out-of-plane or in-plane magnetized sputtered pristine trilayers are compared. Similar irradiation-induced magnetic changes are evidenced in quasi-uniformly focused ion beam or uniformly irradiated films, grown either by sputtering or molecular beam epitaxy. We discuss on plausible common mechanisms underlying the observed effects.
Keywords: ion irradiation, magnetism, perpendicular anisotropy

Publ.-Id: 27774 - Permalink


64Cu-labeled bioconjugates based on triazacyclononane bifunctional chelators for radiopharmaceutical applications
Stephan, H.; Pant, K.; Joshi, T.; Zarschler, K.
The development of multi-functional complexing agents for radiometal nuclides for nuclear medical application represents an intensively studied and rapidly evolving field of research. In this context, multifunctionalisable ligands that can form highly stable metal complexes are of particular interest. Their use enables the simultaneous introduction of radiolabels for nuclear imaging and vector molecules for pharmaceutical targeting.1-2
The tridentate azamacrocycle 1,4,7-triazacyclononane (TACN) is one such ligand that is of special interest for the development of bifunctional chelating agents (BFCAs), TACN forms stable Cu(II)complexes and the azamacrocyclic ligand structure can be easily modified. The introduction of further donor groups on the ligand scaffold, such as pyridine units, significantly enhances the thermodynamic stability as well as the kinetic inertness of the Cu(II) complexes formed. These ligands mostly form Cu(II) complexes with square-pyramidal and distorted octahedral coordination geometry.
Examples of target-specific conjugates (peptides, antibody fragments) and bio(nano)materials equipped with appropriate BFCAs based on TACN (Figure 1), suitable for labeling with 64Cu, will be presented. This enables tumor imaging and biodistribution studies of the materials over a period of days via positron emission tomography (PET).

1. E.W. Price, C. Orvig, Chem. Soc. Rev. 2014, 43, 260. 2. G. Singh, M.D. Gott, H.-J. Pietzsch, H. Stephan, Nuclearmedicine, 2016, 55, 41.
  • Lecture (Conference)
    43rd International Conference on Coordination Chemistry, 30.07.-04.08.2018, Sendai, Japan

Publ.-Id: 27769 - Permalink


Radiolabelled Nanomaterials for Imaging and Treatment of Cancer
Stephan, H.
Novel nanomaterials (NMs) offer excellent prospects for the development of new non-invasive strategies of early diagnosis and efficient monitoring of therapeutic treatments. Thanks to their structural variability, which facilitates setting up the basic structure, modifying the periphery as well as creating complex structures, their properties allow being tailored to both diagnosis and treatment of diseases (theranostic approach) [1]. Provided with special functionalities, NMs allow the simultaneous application of different molecular imaging methods. In the field of cancer medicine, the combination of different imaging techniques such as nuclear (PET: positron emission tomography and SPECT: single-photon emission computed tomography) and near-infrared fluorescence (NIRF) imaging for tracking down tumors and metastases is particularly attractive [2].
This lecture will focus on the development and application of very small radiolabeled NMs, embracing polymeric structures [3] and inorganic particles [4]. Novel strategies will be discussed to develop stealth NMs capable of avoiding biomolecular corona formation and thus evading scavenging of NMs by the mononuclear phagocyte system, leading to eventual accumulation in the liver and spleen [5].

References
[1] J. A. Barreto, W. O’Malley, M. Kubeil, B. Graham, H. Stephan, L. Spiccia, Adv Mater 23 (2011) H18-H40.
[2] G. Singh, M. D. Gott, H.-J. Pietzsch, H. Stephan, Nuklearmedizin 55 (2016) 41-50.
[3] K. Pant, O. Sedláček, R. A. Nadar, M. Hrubý, H. Stephan, Adv Healthcare Mat 6 (2017) 1601115.
[4] K. Zarschler, L. Rocks, N. Licciardello, L. Boselli, E. Polo, K. Pombo Garcia, L. De Cola, H. Stephan, K. A. Dawson, Nanomed-Nanotechnol 12 (2016) 1663-1701.
[5] K. Pombo-García, K. Zarschler, L. Barbaro, J. A. Barreto, W. O’ Malley, L. Spiccia, H. Stephan, B. Graham
Small 10 (2014) 2516-2529.
  • Lecture (others)
    Kolloquium, 26.07.2018, Tokyo, Japan

Publ.-Id: 27768 - Permalink


Union of light ion therapy centers in Europe (ULICE EC FP7) - Objectives and achievements of joint research activities
Pötter, R.; Balosso, J.; Baumann, M.; Bert, C.; Davies, J.; Enghardt, W.; Fossati, P.; Harris, S.; Jones, B.; Krämer, M.; Mayer, R.; Mock, U.; Pullia, M.; Schreiner, T.; Dosanjh, M.; Debus, J.; Orecchia, R.; Georg, D.
Under the umbrella of the European Network for Light Ion Therapy (ENLIGHT), the project on Union of Light Ion Centers in Europe (ULICE), which was funded by the European Commission (EC/FP7), was carried out from 2009 to 2014. Besides the two pillars on Transnational Access (TNA) and Networking Activities (NA), six work packages formed the pillar on Joint Research Activities (JRA). The current manuscript focuses on the objectives and results achieved within these research work packages: "Clinical Research Infrastructure", "Biologically Based Expert System for Individualized Patient Allocation", "Ion Therapy for Intra-Fractional Moving Targets", "Adaptive Treatment Planning for Ion Radiotherapy", "Carbon Ion Gantry", "Common Database and Grid Infrastructures for Improving Access to Research Infrastructures". The objectives and main achievements are summarized. References to either publications or open access deliverables from the five year project work are given. Overall, carbon ion radiotherapy is still not as mature as photon or proton radiotherapy. Achieved results and open questions are reflected and discussed in the context of the current status of carbon ion therapy and particle and photon beam therapy. Most research topics covered in the ULICE JRA pillar are topical. Future research activities can build upon these ULICE results. Together with the continuous increase in the number of particle therapy centers in the last years ULICE results and proposals may contribute to the further growth of the overall particle therapy field as foreseen with ENLIGHT and new joint initiatives such as the European Particle Therapy Network (EPTN) within the overall radiotherapy community.
Keywords: Particle therapy; Proton; Carbon ion; EC project

Publ.-Id: 27766 - Permalink


Is Treatment Benefit caused by specialized oncology Centers in the Treatment of locally advanced Rectal Cancer?
Lattermann, A.; Löck, S.; Jentsch, C.; Weitz, J.; Krause, M.
Fragestellung: Spezialisierte Krebszentren wurden mit dem Ziel einer hochqualitativen Versorgung von Krebspatienten errichtet. Ein entsprechender Benefit wurde bzgl . Patienten mit lokal fortgeschrittenen Rektumkarzinomen bisher nur unzureichend dokumentiert. In der aktuellen Auswertung stellt sich die Frage, inwieweit jene Patienten von
der Behandlung in spezialisierten Krebszentren profitieren. Methodik: Zwischen 2006 und 2013 erhielten insgesamt 131 Patienten mit neu diagnostizierten und histologisch gesicherten Rektumkarzinomen (UICC II, III) eine neoadjuvante Radiochemotherapie. Die nachfolgende Resektion erfolgte in der vom Patienten ausgewählten
Klinik. Anschließend wurde eine adjuvante Chemotherapie durchgeführt. Ein Zentrums-Effekt hinsichtlich des Gesamt- und rezidivfreien Überlebens wurde statistisch mittels Chi-Quadrat- bzw. Log-Rank-Test beurteilt .
Ergebnis: Bei den rekrutierten Patienten fanden sich nach einer medianen Nachbeobachtungszeit von 57 Monaten 8 Patienten (6 %) mit Lokalrezidiv (LR) .
Die operative Behandlung erfolgte im Median 7 Wochen nach beendeter Radiochemotherapie. 3 von 89 Patienten (3,4 %), welche an einem Universitätsklinikum operiert wurden und 5 von 42 Patienten (11,9 %), bei denen die Resektion an einem externen Haus stattfand bekamen ein LR diagnostiziert (p = 0,057). Initial wiesen 7 von 8 Patienten mit späterem LR ein cT4 bzw. cN+ und nur 1 von 8 Patienten ein cT3 bzw . cN0 Stadium auf. Bei allen 8 Patienten wurde bildmorphologisch vor Therapie eine Tumorinfiltration der mesorektalen Faszie beschrieben . 88 % der Patienten mit späterem LR hatten für das präoperative Staging ein CT oder MRT des Beckens erhalten. Bei keinem dieser Patienten zeigte sich eine Änderung des Tumorstadiums. Bei fortbestehendem Infiltrationsverdacht im präoperativen Staging wurde am Universitätsklinikum multiviszeral in Kombination mit anderen Fachrichtungen (Gynäkologie, Urologie), reseziert. Bei allen extern operierten Patienten fand letztendlich eine Standardresektion des Mesorektums, jedoch ohne Beachtung der infiltrierten Organe statt. Entsprechende LR zeigten sich bei allen 8 Patienten genau an jener Stelle, welche als initial infiltrierend beschrieben wurde. Die Zeit von Therapiebeginn bis zur Diagnose des LR betrug bei extern operierten Patienten im Median 21 Wochen, bei intern resezierten 30 Wochen (p = 0,41 Log-Rank Test). Das mediane Überleben betrug bei Patieten mit LR und extern durchgeführter Operation im Median 44 Wochen, bei intern operierten Patienten 87 Wochen (p = 0,043 Log-Rank Test) . Schlussfolgerung: Patienten mit lokal fortgeschrittenen Rektumkarzinomen und fehlendem Ansprechen auf eine neoadjuvante Radiochemotherapie sollten an spezialisierten Zentren mit der Möglichkeit einer multiviszeralen Resektion operiert werden .
  • Abstract in refereed journal
    Strahlentherapie und Onkologie 194(2018), S156-S157

Publ.-Id: 27764 - Permalink


p16 and CD44 as Prognostic Factors for Patients with early Squamous Cell Carcinoma of the Head and Neck Region
Schneider, M.; Linge, A.; Nowak, A.; Gudziol, V.; Olesch, F.; Lohaus, F.; Baretton, G.; Lauer, G.; Zahnert, T.; Baumann, M.; Löck, S.; Krause, M.
Fragestellung: Die kurativ intendierte Therapie von Patienten mit operablen Kopf-Hals-Plattenepithelkarzinomen erfolgt entsprechend der TNM-Klassifikation: Patienten mit lokal fortgeschrittenen, aber funktionell operablen Kopf-Hals-Tumoren erhalten eine postoperative Radio(chemo)therapie, während bei Patienten mit Tumoren im UICC Stadium I und II eine alleinige Operation durchgeführt wird . Dennoch sprechen die Patienten trotz gleichem Tumorstadium und gleicher Histologie heterogen auf die Standardtherapien an . Für atienten mit lokal fortgeschrittenen Tumoren konnte in einer multizentrischen Studie der Radioonkologie-Gruppe des Deutschen Konsortiums für Translationale Radioonkologie (DKTK-ROG) gezeigt werden, dass der HPV-Status und weitere Biomarker, wie beispielsweise Krebsstammzellmarker und Hypoxie-assoziierte Gensignaturen, wichtige Prognosefaktoren für die lokoregionale Tumorkontrolle nach postoperativer Radiochemotherapie darstellen . Diese Studie hat das Ziel zu untersuchen, ob dieselben prognostischen Faktoren auch für Patienten mit lokal begrenzten Tumoren relevant sind, die eine alleinige Operation erhalten.
Methodik: In dieser retrospektiven, monozentrischen Studie wurden 174 Patienten mit einem zwischen 2005 bis 2014 diagnostizierten lokal begrenzten Plattenepithelkarzinom (Mundhöhle, Oropharynx, Hypopharynx) eingeschlossen, die eine alleinige Operation in kurativer Intention erhalten haben . Die Proteinexpressionen des HPV-Surrogatmarkers 16 und des Krebsstammzellmarkers CD44 wurden immunhistochemisch bestimmt . Der HPV DNA Nachweis erfolgte mittels eines PCR-basierten Arrays. Enexpressionsanalysen des Markers CD44 sowie von Hypoxie-assoziierten Gensignaturen wurden mittels nanoString-Technologie durchgeführt . Endpunkte waren die lokale Tumorkontrolle (LK) und die regionale Tumorkontrolle (RK) . Ergebnisse: Alle Patienten mit p16-positiven Tumoren zeigten eine vollständige RK im Vergleich zu den Patienten mit p16-negativen Tumoren (p = 0,102) . Es konnten aber nur 27,3 % der p16-positiven Tumoren positiv für HPV DNA getestet werden (22,7 % HPV16 DNA; 4,5 % HPV33 DNA) . Patienten mit CD44-positiven Tumoren zeigten eine schlechtere LK als Patienten mit CD44-negativen Tumoren, insbesondere war eine hohe CD44-Positivität der Tumorzellen (>65 % der Tumorzellen) signifikant mit dem Auftreten von Lokalrezidiven assoziiert (p = 0,005) . Eine erhöhte CD44-Genexpression zeigte ebenfalls eine signifikant schlechtere LK (p = 0,036) . Die Analyse von Hypoxie-assoziierten Gensignaturen zeigte jedoch keinen Einfluss auf die Endpunkte.
Schlussfolgerung: Diese Analysen zeigen, dass p16 und CD44 auch bei lokal begrenzten Tumoren potentielle prognostische Biomarker darstellen und, nach erfolgreicher Validierung in der aktuell rekrutierenden HNbioSUR-Studie, möglicherweise für die Individualisierung der Therapie eingesetzt werden können.
  • Abstract in refereed journal
    Strahlentherapie und Onkologie 194(2018), S132

Publ.-Id: 27763 - Permalink


A coronene-based semiconducting two-dimensional metal-organic framework with ferromagnetic behavior
Dong, R.; Zhang, Z.; Tranca, D. C.; Zhou, S.; Wang, M.; Adler, P.; Liao, Z.; Liu, F.; Sun, Y.; Shi, W.; Zhang, Z.; Zschech, E.; Mannsfeld, S.; Felser, C.; Feng, X.
Metal–organic frameworks (MOFs) have so far been highlighted for their potential roles in catalysis, gas storage and separation. However, the realization of high electrical conductivity (>10^−3  S cm^−1) and magnetic ordering in MOFs will afford them new functions for spintronics, which remains relatively unexplored. Here, we demonstrate the synthesis of a two-dimensional MOF by solvothermal methods using perthiolated coronene as a ligand and planar iron-bis(dithiolene) as linkages enabling a full π-d conjugation. This 2D MOF exhibits a high electrical conductivity of ~10 S cm−1 at 300 K, which decreases upon cooling, suggesting a typical semiconductor nature. Magnetization and 57Fe Mössbauer experiments reveal the evolution of ferromagnetism within nanoscale magnetic clusters below 20 K, thus evidencing exchange interactions between the intermediate spin S = 3/2 iron(III) centers via the delocalized π electrons. Our results illustrate that conjugated 2D MOFs have potential as ferromagnetic semiconductors for application in spintronics.

Publ.-Id: 27760 - Permalink


Kinematic dynamo action of a precession driven flow based on the results of water experiments and hydrodynamic simulations.
Giesecke, A.; Vogt, T.; Gundrum, T.; Stefani, F.
The project DRESDYN (DREsden Sodium facility for DYNamo and thermohydraulic studies) conducted at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) provides a new platform for a variety of liquid sodium experiments devoted to problems of geo- and astrophysical magnetohydrodynamics. The most ambitious experiment within this project is a precession driven dynamo experiment that currently is under construction. It consists of a cylinder filled with liquid sodium that simultaneously rotates around two axes. The experiment is motivated by the idea of a precession-driven flow as a complementary energy source for the geodynamo or the ancient lunar dynamo.

In the present study we address numerical and experimental examinations in order to identify parameter regions where the onset of magnetic field excitation will be most probable. Both approaches show that in the strongly nonlinear regime the flow is essentially composed of the directly forced primary Kelvin mode and higher modes in terms of standing inertial waves that arise from nonlinear self-interactions. A peculiarity is the resonance-like emergence of an axisymmetric mode that represents a double roll structure in the meridional plane, which, however, only occurs in a very limited range of the precession ratio. This axisymmetric mode turns out to be beneficial for dynamo action, and kinematic simulations of the magnetic field evolution induced by the time-averaged flow exhibit magnetic field excitation at critical magnetic Reynolds numbers around ${\rm{Rm}}^{\rm{c}}\approx 430$, which is well within the range of the planned liquid sodium experiment.
Keywords: Dynamo DRESDYN

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  • Secondary publication expected from 20.08.2019

Publ.-Id: 27759 - Permalink


Protracted river recovery from medieval earthquakes
Stolle, A.; Schwanghart, W.; Andermann, C.; Bernhardt, A.; Fort, M.; Wittmann, H.; Merchel, S.ORC; Rugel, G.; Adhikary, B. R.; Korup, O.
Mountain rivers respond to strong earthquakes by rapidly aggrading to accommodate excess sediment delivered by co-seismic landslides. Detailed sediment budgets indicate that rivers need several years to decades to recover from such seismic disturbances, depending on how recovery is defined. We examine several proxies of river recovery around Pokhara, Nepal’s second largest city. We use a freshly exhumed cohort of floodplain trees in growth position as a geomorphic marker of rapid sedimentation that formed a fan covering 148 km² in a Lesser Himalayan basin with tens of meters of debris. Radiocarbon dates of these buried trees are consistent with those of nearby valley fills linked to major Himalayan earthquakes during medieval times, and offer benchmarks for estimating average rates of sedimentation and re-incision. We combine high-resolution digital elevation data, geodetic field surveys, aerial photos documenting historic channel changes, estimated removed volumes, calculated long-term denudation rates, and dated re-exhumed tree trunks to reconstruct dated geomorphic marker surfaces. The volumes of sediment lost from these surfaces require net sediment yields of up to 4200 t km² yr¹, averaged over some 650 years since the last inferred earthquake. These rates exceed density-adjusted rates of catchment-wide denudation derived from concentrations of cosmogenic ¹⁰Be in river sands. The lithological composition of active channel-bed load differs from that of local bedrock, confirming that rivers are still mainly evacuating medieval valley fills, locally incising at rates of 160 to 220 mm yr¹ in the past 50 years. Pronounced knickpoints and epigenetic gorges at tributary junctions add to the picture of a protracted fluvial response; only the distal portions of the earthquake-derived sediment wedge have been incised to near their base. Our results challenge the notion that mountain rivers recover from earthquakes within years to decades. The valley fills around Pokhara document that even highly erosive Himalayan rivers need at least centuries to millennia to adjust. Our results motivate some rethinking of post-seismic hazard appraisals and infrastructural planning in mountain regions.
Keywords: accelerator mass spectrometry, cosmogenic nuclide, geomorphological risk assessment, Earthquake
  • Poster
    4th Central European Geomorphology Conference, 09.-13.10.2017, Bayreuth, Deutschland

Publ.-Id: 27757 - Permalink


Dynamics of nanoparticle morphology under low energy ion irradiation
Holland-Moritz, H.; Graupner, J.; Möller, W.; Pacholski, C.; Ronning, C.
If nanostructures are irradiated with energetic ions, the mechanism of sputtering becomes important when the ion range matches about the size of the nanoparticle. Gold nanoparticles with diameters of ∼50 nm on top of silicon substrates with a native oxide layer were irradiated by gallium ions with energies ranging from 1 to 30 keV in a focused ion beam system. High resolution in situ scanning electron microscopy imaging permits detailed insights in the dynamics of the morphology change and sputter yield. Compared to bulk-like structures or thin films, a pronounced shaping and enhanced sputtering in the nanostructures occurs, which enables a specific shaping of these structures using ion beams. This effect depends on the ratio of nanoparticle size and ion energy. In the investigated energy regime, the sputter yield increases at increasing ion energy and shows a distinct dependence on the nanoparticle size. The experimental findings are directly compared to Monte Carlo simulations obtained from iradina and TRI3DYN, where the latter takes into account dynamic morphological and compositional changes of the target.
Keywords: in situ ion beam, Monte Carlo, nanoparticles, sputtering

Publ.-Id: 27756 - Permalink


Frequency linewidth and decay length of spin waves in curved magnetic membranes
Otalora, J. A.; Kákay, A.; Lindner, J.; Schultheiss, H.; Thomas, A.; Fassbender, J.; Nielsch, K.
The curvature of a magnetic membrane was presented as a means of inducing nonreciprocities in the spin-wave (SW) dispersion relation [see Otalora et al. Phys. Rev. Lett. 117, 227203 (2017) and Otalora et al. Phys. Rev. B 95, 184415 (2017)], thereby expanding the toolbox for controlling SWs. In this paper, we further complement this toolbox by analytically showing that the membrane curvature is also manifested in the absorption of SWs, leading to a difference in the frequency linewidth (or lifetime) of counterpropagating magnons. Herein, we studied the nanotubular case, predicting changes of approximately greater than 10% and up to 20% in the frequency linewidth of counterpropagating SWs for a wide range of nanotube radii ranging from 30 nm to 260 nm and with a thickness of 10 nm. These percentages are comparable to those that can be extracted from experiments on heavy metal/magnetic metal sandwiches, wherein linewidth asymmetry results from an interfacial Dzyaloshinskii-Moriya interaction (DMI). We also show that the interplay between the frequency linewidth and group velocity leads to asymmetries in the SW decay length, presenting changes between 10% and 22% for counterpropagating SWs in the frequency range of 2-10 GHz. For the case of the SW dispersion relation, the predicted effects are identified as the classical dipole-dipole interaction, and the analytical expression of the frequency linewidth has the same mathematical form as in thin films with the DMI. Furthermore, we present limiting cases of a tubular geometry with negligible curvature such that our analytical model converges to the case of a planar thin film known from the literature. Our findings represent a step forward toward the realization of three-dimensional curvilinear magnonic devices.
Keywords: FERROMAGNETIC-RESONANCE LINEWIDTH; WEAK FERROMAGNETISM; MORIYA INTERACTION; THIN-FILMS; MAGNONICS

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Publ.-Id: 27753 - Permalink


Creation of silicon vacancy in silicon carbide by proton beam writing toward quantum sensing applications
Ohshima, T.ORC; Satoh, T.; Kraus, H.; Astakhov, G. V.ORC; Dyakonov, V.ORC; Baranov, P. G.
Single photon source (SPS) is a key element for quantum spintronics and quantum photonics. It is known that several color centers such as silicon vacancy (VSi), divacancy (VSiVC), carbon antisite carbon vacancy pair (CSiVC), in silicon carbide (SiC) act as SPSs. Spin (S = 3/2) in VSi in SiC can be manipulated even at room temperature and the intensity of its photoluminescence (PL) changes depending on the spin states (mS = ±3/2 or mS = ±1/2). Since PL from VSi is in the near infrared region (around 900 nm), it is expected that VSi is applied to quantum sensor especially for biological or medical applications. In this review, we discuss quantum sensing based on VSi in SiC. Also, we discuss energetic particle irradiation, especially proton beam writing (PBW), in which proton microbeams with MeV range are used, as a method to create VSi in SiC since PBW can create VSi in certain locations with micrometer accuracy and this is very useful to introduce VSi in electronic devices without the degradation of their electrical characteristics.

Publ.-Id: 27748 - Permalink


The role of incidence angle in the morphology evolution of Ge surfaces irradiated by medium-energy Au ions
Dell’Anna, R.; Iacob, E.; Barozzi, M.; Vanzetti, L.; Hübner, R.; Böttger, R.; Giubertoni, D.; Pepponi, G.
Germanium (Ge) surfaces have been irradiated with 26 keV gold (Au) ions at a constant fluence and at incidence angles varying from 0° to 85°. The evolution of the emerging nanostructures is studied by atomic force microscopy (AFM), scanning electron microscopy, x-ray photoelectron spectroscopy (XPS), and cross-sectional transmission electron microscopy. The obtained results are compared with findings reported in the literature. Periodic rippled patterns with the wave vector parallel to the projection of the ion beam direction onto the Ge surface develop between 30° and 45°. From 75° the morphology changes from parallel-mode ripples to parallel-mode terraces, and by further increasing the incidence angle the terraces coarsen and show a progressive break-up of the front facing the ion beam. No perpendicular-mode ripples or terraces have been observed. The analysis of the AFM height profiles and slope distributions shows in the 45°-85° range an angular dependence of the temporal scale for the onset of nonlinear processes. For incidence angles below 45°, the surface develops a sponge-like structure, which persists at higher incidence angles on the top and partially on the face of the facets facing the ion beam. The XPS and the energy-dispersive x-ray spectroscopy evidence the presence of Au nano-aggregates of different sizes for the different incidence angles. This study points out the peculiar behavior of Ge surfaces irradiated with medium-energy Au ions and warns about the differences to be faced when trying to build a universal framework for the description of semiconductor pattern evolution under ion-beam irradiation.
Keywords: ion beam irradiation, germanium, gold ions, binary system, ripples, terraces, sponge-like structures

Publ.-Id: 27746 - Permalink


A versatile ion beam spectrometer for studies of ion interaction with 2D materials
Schwestka, J.; Melinc, D.; Heller, R.; Niggas, A.; Leonhartsberger, L.; Winter, H.; Facsko, S.; Aumayr, F.ORC; Wilhelm, R. A.ORC
We present an ultra-high vacuum setup for ion spectroscopy of freestanding two-dimensional solid targets. An ion beam of different ion species (e.g. Xe with charge states from 1 to 44 and Ar with charge states from 1 to 18) and kinetic energies ranging from a few 10 eV to 400 keV is produced in an electron beam ion source. Ions are detected after their transmission through the 2D target with a position sensitive microchannel plate detector allowing the determination of the ions exit charge state as well as the scattering angle with a resolution of approx. 0.04◦. Further, the spectrometer is mounted on a swiveling frame covering a scattering angle of ±8° with respect to the incoming beam direction. By utilizing a beam chopper we measure the time-of-flight of the projectiles and determine the energy loss when passing a 2D target with an energy uncertainty of about 2%. Additional detectors are mounted close to the target to observe emitted secondary particles and are read-out in coincidence with the position and time information of the ion detector. A signal in these detectors can also be used as a start trigger for time-of-flight measurements, which then yield an energy resolution of 1% and an approx. 1000-fold larger duty cycle. First results on the interaction of slow Xe30+ ions with a freestanding single layer of graphene obtained with the new setup are compared to recently published data where charge exchange and energy were measured by means of an electrostatic analyzer.
Keywords: slow highly charged ions, 2D materials, ion spectrometer, single layer graphene

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Publ.-Id: 27743 - Permalink


Neutralization Dynamics of Slow Highly Charged Ions in 2D Materials
Wilhelm, R.ORC; Gruber, E.ORC; Schwestka, J.; Heller, R.; Fascko, S.; Aumayr, F.ORC
We review experimental and theoretical work on the interaction of slow highly charged ions with two-dimensional materials. Earlier work in the field is summarized and more recent studies on 1 nm thick amorphous carbon nanomembranes and freestanding single layer graphene by the authors are reviewed. To explain the findings, models for energy loss determination as well as qualitative model descriptions for the observed ultrafast neutralization dynamics are discussed. The results shown in this paper will be put into context with findings of nanostructure formation on two-dimensional materials, both freestanding and on substrate, as well as on surfaces of bulk insulators.
Keywords: low energy ions; highly charged ions; 2D materials

Publ.-Id: 27742 - Permalink


Working in stealth mode: Towards the development of biomolecular corona-resistant hydrophilic nanomaterials for biomedical applications
Joshi, T; Nsubuga, A.; Zarschler, K.; Stephan, H.
The interaction of nanoparticles (NPs) with biomolecules depends on their surface characteristics and has a major influence on their ultimate metabolic fate. Attempts to modulate the NP-biomolecule interaction in complex biological conditions has led to intensive research on the role of NP size, shape, charge, surface structure and the capping molecules in their eventual pharmacokinetic response. Research shows that to avoid accumulation in the organs of the mononuclear phagocyte system (MPS), engineered NPs must resist nonspecific adsorption of proteins (biomolecular corona) onto their surface. To date the most common approach to make NPs corona-resistant includes formation of a hydrophilic, neutral-charged polyethylene glycol coating (PEGylation) on their surface. This route, widely used by many groups, furnishes hydrophilic NPs, but suffers from some serious drawbacks, such as, a substantial increase in the hydrodynamic diameter (Dh) after PEGylation, and the formation of anti-PEG antibodies in vivo.
Herein, we present our efforts towards tackling the problem of biomolecular corona formation. To this end, we have explored the use of amphiphilic zwitterionic polymers and low molecular weight entities as capping ligands on the surface of ultrasmall iron oxide nanoparticles (USPIONs) and lanthanide-doped upconverting nanoparticles (UCNPs). Following such surface modification, the hydrophobic NPs were rendered water-dispersible and showed reduced adsorption of serum proteins, but without any significant increase in particle size. Additionally, the availability of reactive functional groups on the surface of the modified NPs makes them ready for further functionalization with, for example, small molecules, peptides, proteins, and antibodies. The presented results highlight the usefulness of our surface functionalization strategy to produce biocompatible materials suitable for multimodal diagnostic/therapeutic applications.
  • Invited lecture (Conferences)
    256th ACS National Meeting in Boston, MA, 19.-23.08.2018, Boston, USA

Publ.-Id: 27741 - Permalink


Development of biomolecular corona-resistant nanomaterials suitable for biological applications
Joshi, T.; Nsubuga, A.; Zarschler, K.; Stephan, H.
Nanoparticle (NP) size, shape, charge, surface structure and the capping moieties have a significant influence on their eventual pharmacokinetic behaviour. For NPs to avoid accumulation in the organs of the mononuclear phagocyte system (MPS), it is important that they resist nonspecific adsorption of proteins (biomolecular corona) onto their surface. Reported methods to make corona-resistant hydrophilic NPs mostly suffer from serious drawbacks in regards to the in vivo applications of the engineered NMs. The major ones being (1) substantial increase in the hydrodynamic diameter (Dh) of the modified NMs, and (2) the formation of anti-PEG antibodies in vivo. Herein, we will present our efforts towards tackling the problem of biomolecular corona formation in ultrasmall iron oxide nanoparticles (USPIONs) and lanthanide-doped upconverting nanoparticles (UCNPs) by using amphiphilic zwitterionic polymers and low molecular weight entities as capping ligands on the NP surface. Our studies show that such surface functionalization strategy can produce biocompatible NPs that exhibit negligible interaction with biomolecules, and are suitable for developing multimodal imaging/therapeutic agents.
  • Invited lecture (Conferences)
    10th International Symposium on Nano & Supramolecular Chemistry, 09.-12.07.2018, Dresden, Germany

Publ.-Id: 27740 - Permalink


Nonlinear THz Spectroscopy of Two-Dimensional Systems
Helm, M.; König-Otto, J.; Schmidt, J.; Dimakis, E.; Winnerl, S.; Schneider, H.
Nonlinear THz experiments using a free-electron laser are presented on Landau quantized graphene as well as on intersubband transitions in a single GaAs quantum well.
Keywords: terahertz, free electron laser, graphene, Landau Levels, intersubband, GaAs, quantum well
  • Invited lecture (Conferences)
    Frontiers of photonics, plasmonics and electronics with 2D nanosystems, 14.-20.07.2018, Erice, Italy
  • Invited lecture (Conferences)
    Advanced Electromagnetics Symposium (AES 2018), 24.06.-01.07.2018, Marseille, France

Publ.-Id: 27737 - Permalink


Design of high-temperature solar-selective coatings based on aluminium titanium oxynitrides AlyTi1-y(OxN1-x). Part 2: Experimental validation and durability tests at high temperature
Escobar-Galindo, R.; Guillén, E.; Heras, I.; Rincón-Llorente, G.; Alcón-Camas, M.; Lungwitz, F.; Munnik, F.; Schumann, E.; Azkona, I.; Krause, M.
The durability of two solar-selective aluminium titanium oxynitride multilayer coatings was studied under conditions simulating realistic operation of central receiver power plants. The coatings were deposited by cathodic vacuum arc applying an optimized design concept for complete solar-selective coating (SSC) stacks. Compositional, structural and optical characterization of initial and final stacks was performed by scanning electron microscopy, elastic recoil detection, UV-Vis-NIR-IR spectrophotometry and X-Ray diffraction. The design concept of the solar selective coatings was validated by an excellent agreement between simulated and initial experimental stacking order, composition and optical properties.

Both SSC stacks were stable in single stage tests of 12 hours at 650°C. At 800°C, they underwent a structural transformation by full oxidation and they lost their solar selectivity. During cyclic durability tests, multilayer 1, comprised of TiN, Al0.64Ti0.36N and an Al1.37Ti0.54O top layer, fulfilled the performance criterion (PC) ≤ 5% for 300 symmetric, 3 hours long cycles at 600°C in air. Multilayer 2, which was constituted of four AlyTi1-y(OxN1-x) layers, met the performance criterion for 250 cycles (750 hours), but was more sensitive to these harsh conditions. With regard to the degradation mechanisms, the coarser microstructure of multilayer 1 is more resistant against oxidation than multilayer 2 with its graded oxygen content. These results confirm that the designed SSCs based on AlyTi1-y(OxN1-x) materials withstand breakdown at 600ºC in air. Therefore, they can be an exciting candidate material for concentrated solar power applications at high temperature.
Keywords: Solar selective coatings, thermal stability, optical properties, concentrated solar power, optical simulation, oxynitrides

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  • Secondary publication expected from 23.04.2019

Publ.-Id: 27734 - Permalink


Cluster tool for in situ processing and comprehensive characterization of thin films at high temperatures
Wenisch, R.; Lungwitz, F.; Hanf, D.; Heller, R.; Zscharschuch, J.; Hübner, R.; von Borany, J.; Abrasonis, G.; Gemming, S.; Escobar Galindo, R.; Krause, M.
A new cluster tool for in situ real-time processing and depth-resolved compositional, structural and optical characterization of thin films at temperatures from -100 to 800 °C is described. The implemented techniques comprise magnetron sputtering, ion irradiation, Rutherford backscattering spectrometry, Raman spectroscopy and spectroscopic ellipsometry. The capability of the cluster tool is demonstrated for a layer stack MgO/ amorphous Si (~60 nm)/ Ag (~30 nm), deposited at room temperature and crystallized with partial layer exchange by heating up to 650°C. Its initial and final composition, stacking order and structure were monitored in situ in real time and a reaction progress was defined as a function of time and temperature.
Keywords: Cluster tool, thin films, in situ, high temperature, Rutherford backscattering, Raman spectroscopy, ellipsometry, metal-induced crystallization

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  • Secondary publication expected from 31.05.2019

Publ.-Id: 27732 - Permalink


Phytotoxicity of polymetallic mine wastes from southern Tuscany and Saxony
Franzaring⁠⁠, J.; Ancora⁠, S.; Paoli⁠, L.; Fongoh⁠, A. H.; Büttner⁠, P.; Fangmeier⁠, A.; Schlosser⁠, S.; Monaci, F.
Restoration potential of mine wastes or approaches to improve soil conditions and to ameliorate phytotoxicity on these sites may be simulated in standardized greenhouse experiments. Plants can be cultivated side by side on materials from different origins in dilution series with defined admixtures of certain aggregates. Mine wastes used in the present study originated from Fenice Capanne (FC, Tuscany, Italy) and Altenberg (ALT, Saxony, Germany). Tailings of the Italian site contain high concentrations of lead, zinc, arsenic and sulphur while tin, wolfram, molybdenum and lithium are highly elevated in the German mine waste. We tested growth responses of five crop species and analyzed concentrations of various metals and nutrients in the shoot to evaluate the toxicity of the FC mine waste and found oilseed rape being the most and corn the least resistant crop. Interestingly, oilseed rape accumulated seven times higher levels of lead than corn without showing adverse effects on productivity. In a subsequent comparison of FC and ALT mine waste, we cultivated different species of buckwheat (Fagopyrum spec.), a fast growing genus that evolved in mountain areas and that has been shown to be tolerant to low pH and high concentrations of metals. We found that the FC mine waste was more toxic than the ALT substrate in F. tataricum and F. esculentum. However, lower admixtures of FC material (10%) resulted in stronger growth reductions than higher proportions (25%) of the mine waste which was primarily related to the slightly lower pH and higher availability of essential metals due to the admixture of sand. These results confirm the importance of managing the soil chemical and physical characteristics of wastelands and call for the development of assisted reclamation to prepare sites for regular biomass production.
Keywords: Mine wastes, Phytoremediation, Heavy metals, Oilseed rape, Buckwheat, Soil amendment

Publ.-Id: 27721 - Permalink


Stability of melt flow during magnetic sonication in a floating zone configuration
Grants, I.; Gerbeth, G.
This paper considers the linear stability of a liquid metal flow driven by superimposed alternating and static axial magnetic fields in the floating zone configuration. A simple model is constructed that assumes a slight axial variation of the flow-driving radial magnetic force and a low-to-moderate skin effect. This force drives two symmetrical flow tori. Formation of the field-parallel layer is observed for a strong static field. In this regime the instability sets in as a standing azimuthal wave around the circumference of the cylindrical melt volume near its midplane. The length of this wave scales with the thickness of the parallel layer. The instability criterion may be formulated in terms of an interaction parameter reaching its critical value at around 525.
Keywords: -

Publ.-Id: 27720 - Permalink


High-speed X-ray CT imaging of a strongly cavitating nozzle flow
Bauer, D.; Barthel, F.; Hampel, U.
Examining or imaging of internal structures in flows with cavitation is still one of the greatest challenges in this field of research. In a specially designed nozzle, a strong cavitation region (CR) is generated with a liquid core (LC) in the center, surrounded by vapour. While it is almost not feasible to visualize the inside of the CR with visible light, it is shown that with high-speed X-ray computed tomography it is possible to visualize the dynamics of the unsteady cavitational flow structures inside the CR. The observed phenomena start with a ring of cavitation and small amounts of vapour inside the LC at / near the entrance of the cavitation channel. Further downstream the cavitation is growing rapidly and cavitation structures, as string cavitation can be identified inside the LC. In addition the results are compared with former time averaged CT images of the same nozzle and with results obtained with high-speed videography.
Keywords: Cavitation Flow, ROFEX, Ultrafast X-ray CT

Publ.-Id: 27719 - Permalink


Development of a novel target module redirecting UniCAR T cells to Sialyl Tn-expressing tumor cells
Loureiro, L.; Feldmann, A.; Bergmann, R.; Koristka, S.; Berndt, N.; Arndt, C.; Pietzsch, J.; Novo, C.; Videira, P.; Bachmann, M.
The development of antibody-based therapies has been driven by progress in the immune response field culminating in the development of chimeric antigen receptors (CARs) as a promising approach in cancer immunotherapy. Nevertheless, drawbacks associated with CAR T cell therapies include on-target off-tumor effects or severe toxicity. Recently, we developed a novel modular universal CAR (UniCAR) platform to increase clinical safety while maintaining the efficacy of CAR T cell therapy. UniCAR T cells are exclusively activated via a target module (TM) that allows the cross-link between UniCAR T cells and target cancer cells. Here, we describe a novel TM against the tumor-associated carbohydrate antigen sialyl-Tn (STn). The developed anti-STn TM efficiently activate and redirect UniCAR T cells to STn-expressing tumors in a highly efficient target-specific and target-dependent manner, promoting the secretion of pro-inflammatory cytokines, tumor cell lysis of breast and bladder cancer cells in vitro and of breast cancer cells in experimental mice. Additionally, PET-imaging shows that anti-STn TM is enriched at the tumor site representing the potential use of this TM in diagnostic imaging. Taken together, these data demonstrate the effective and potential use of this CAR T cell-derived modular system to target STn in different types of cancer.
Keywords: Immunotherapy, CAR T cell therapy, Sialyl-Tn (STn)

Publ.-Id: 27716 - Permalink


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